Transmission control system

ABSTRACT

There is disclosed a control system providing manual and also automatic shift control for a multispeed forward and reverse track-laying vehicle transmission. The automatic operation is provided by pilot valves which are controlled by a pressure indicative of vehicle speed and also a pressure indicative of engine torque demand to condition shift valves to effect shifting between all of the forward drives. The manual control is provided by solenoid valve control over the bias of the shift valves to effect manual shifting with downshifting to lower speed range drives being delayed until vehicle speed is suitable for the speed range of the selected lower drive. The transmission includes a torque converter having a lockup clutch whose engagement is effected with the fluid delivery used for the selected drive engagement with the lockup clutch engagement being momentarily interrupted on shifting between certain of the forward drives by shuttle valve operation. A neutral valve whose operation is controlled by solenoid valves operates to deliver fluid to the shift valves for the drive engagements and on interruption of electrical power to its solenoid valves, operates to automatically condition the transmission in neutral but if the transmission is providing drive and there then occurs loss of power to these solenoid valves, the neutral valve continues to permit the establishment of transmission drive. The control system further includes a directional valve which is operated by solenoid valves to control the engagement of devices that are necessary to establish forward and reverse drive. When there is loss of power to the directional valve&#39;&#39;s solenoid valves, the directional valve remains in its preselected position. A forwardreverse inhibitor valve prevents the directional valve from effecting shifting between forward and reverse above a vehicle speed suitable for such shifting. The control system also includes a brake coolant valve which is controlled by a brake apply valve to deliver fluid to cool the transmission&#39;&#39;s two output brakes with a normal fluid supply that originates at an input driven pump and is supplemented by operation of a diverter valve that delivers flow from output pump after higher fluid supply priorities are set.

United States Patent Thompson 1 Dec. 12, 1972 [54] TRANSMISSION CONTROLSYSTEM [57] ABSTRACT Inventor: Charles R Thompson Pittsboro, There isdisclosed a control system providing manual Ind. and also automaticshift control for a multispeed forward and reverse end vehicletransmission. The auto- [73] Asslgnee g z r Corpuranon matic operationis provided by pilot valves which are e rm 1c controlled by a pressureindicative of vehicle speed [22] Filed: Feb. 12, 1971 and alsoa'pressure indicative of engine torque demand to condition shift valvesto effect shifting [21'] Appl 114386 between all of the forward drives.The manual control is provided by solenoid valve control over the biasof [52] us. Cl. 192/4, 74/869, 74/7205 the shift valves to effect manualShifting with 511' 1nt.Cl ..F16h 37/06 downshifting to lower speed rangedrives being 53] Field f Search 74 35 9 delayed until vehicle speed issuitable for the speed B60k/21/00; F16d/67/O4 range of the selectedlower drive. The transmission includes a torque converter having alockup clutch [56] Reienmes Cited whose engagement is effected with thefluid delivery used for the selected drive engagement with the UNlTEDSTATES PATENTS lockup clutch engagement being momentarily interrupted onshifting between certain of the forward 32223: drives by shuttle valveoperation. A neutral valve Primary ExaminerArthur I. McKeon Attorney-W.E. Finken, A. M. Heiter and R. L. Phillips whose operation is controlledby solenoid valves operates to deliver fluid to the shift valves for thedrive engagements and on interruption of electrical power to itssolenoid valves, operates to 15 Claims, 7 Drawing Figures V PATENTEDI973 3.705.642

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J BY l 51 a! ATTORNEY PATENTED I97? 3. 705 642 I sum u or 5 MAN UA LVALV E PRlORlTY VALVE |-2 TRIMMER INVEA'TOR 3:152 5 WE CZzar/esHJhompson W farm 42 AHORNI Y 1 TRANSMISSION CONTROL SYSTEM Theinvention herein described was made in the course of work under acontract or subcontract thereunder with the Department of the Army.

This invention relates to transmission control systems and moreparticularly to control systems providing manual and also automaticshift control for track-laying vehicle transmissions.

The transmission controlled by this system provides four forward drivesand two reverse drives and the control system according to the presentinvention has provision for providing automatic control of all theforward drives and manual control of the three lowest forward speedrange drives and the two reverse drives. The control system includes aninput driven pump, an upstream main pressure regulator valve, adownstream secondary main pressure regulator valve anda downstreamsupercharge pressure regulator valve. For automatic operation, pilotvalves are provided which are each biased to demand an upshift by agovernor pressure indicative of vehicle speed which is .opposed by aT.V. pressure that is derived from secondary main line pressure and isindicative of torque demand. The pilot valves control pressure biaschambers of spring biased shift valves to condition the shift valves toeffect automatic shifting using main line pressure. The manual controlof shifting between the three lowest speed range forward drives isprovided by solenoid valves which operate to control the pressure biaschainbers of the associated shift valves. In manual selection, asolenoid valve controlled manual valve delivers secondary main linepressure to provide a downshift bias on all of the pilot valves whicheffectively prevents automatic upshifts during manually selected driveoperation. When manual downshifts are selected at an unsuitably highvehicle speed, governor pressure acts to hold the higher speed rangepilot valve in its upshift demand position until the speed decreases toa suitable value. The fluid delivery for drive establishment is cascadedthrough the shift valves starting with the highest speed range driveshift valve so that the lower speed range shift valves may be shiftedbut do not receive fluid until the higher speed range shift valve isdownshifted.

The transmission includes a lockup clutch whose engagement is madepossible by the present control system in all forward drives above thelowest speed range forward drive. Automatic engagement occurs under thecontrol of a lockup shift valve which has a governor pressure biasopposed by a T.V. pressure bias. The fluid delivery for the lockupclutch originates with the lines feeding fluid supply for engagement ofthe second, third and fourth forward drives and these lines are passedthrough a series of timer valves with one of these valves alternatelyshuttling during shifting to momentarily interrupt the fluid pressuredelivery to the lockup clutch to effect momentary interruption of itsengagement during the shifting.

A neutral valve controls the delivery of main line pressure to all ofthe shift valves, the neutral valve being spring biased away froma driveposition toa neutral position preventing such fluid delivery and havingsolenoid valve controlled pressure chambers at each end for normallycontrolling its positioning. The neutral valve is constructed so that ifthere is power interruption to both of its solenoid valves, the valve isheld by its spring bias in its neutral position preventing driveestablishment. Alternatively, when the neutral valve is in its driveposition for effecting drive establishment and on such powerinterruption to the solenoid valves, the neutral valve is maintained inits drive position for continued vehicle drive.

A directional valve controls the establishment of the transmission driveestablishing devices effecting forward and reverse and is normallycontrolled by solenoid valves to control the establishment of thesedevices and thus determine the direction of vehicle travel. Aforward-reverse inhibitor valve is controlled by governor pressureindicative of vehicle output speed to control whether the directionalvalve can be moved by the normal operation of its solenoid valves todetermine either forwarder reverse drive and thus determines whethershifting between forward and reverse can occur. The forward-reverseinhibitor valve is used to defeat shifts by the directional valve tothus prevent shifting between forward and reverse at an unsuitably highvehicle speed. In the event there is loss of power to both the solenoidvalves controlling the directional valve, there is no immediate effecton the position of the directional valve so that it maintains thepreselected drive direction.

A brake coolant valve provides for delivering fluid to cool thetransmissions two output brakes. An output pump push start-divertervalve operates to deliver fluid from an output driven pump for mainpressure supply in the two lowest speed range forward drives for pushstarting and diverts the fluid for output brake cooling during outputbrake engagement provided the input pump is supplying sufficient fluidfor the system s other demands.

An object of the present invention is to provide a new and improvedtransmission control system.

Another object is to provide a. new and improved transmission controlsystem providing both manual and automatic shifting.

Another object is to provide a transmission control system having amanual shift control and an automatic shift control with the automaticshifting accomplished under the control of pilot valves and withsolenoid valve manual .overcontrol and manual downshifting prevented bythe pilot valves above certain speeds.

Another object is to provide in a. transmission control system adirectional valve that provides for engagement of the transmissions'sforward and reverse drive establishing devices and is prevented fromaccomplishing forward-reverse shifting by a shift inhibitor valve underthe control of vehicle speed.

Another object is to provide in a transmission control system a fluiddelivery valve for determining fluid delivery to establish drive underthe control of solenoid valves which upon power interruption thereto donot affect preselected fluid delivery operation of the fluid deliveryvalve.

Another object is to provide in a transmission control system adirectional valve for determining shifting between forward and reverseunder the control of solenoid valves which upon power interruptionthereto do not affect the preselected operation of the directionalvalve.

These and other objects of the present invention will be more apparentfrom the following description and drawings in which:

A transmission and a control system therefor according to the presentinvention are shown schematically in FIGS. 2, 3, 4, 5 and 6 whenarranged as indicated by FIG. 1.

FIG. 7 shows the schedule of transmission operation.

TRANSMISSION ARRANGEMENT The invention is illustrated in an arrangementcontrolling a track-laying vehicle transmission which is capable ofproviding multiple speed ranges and also hydrostatic steering operationin both forward and reverse. The transmission arrangement generallycomprises a prime mover driven input shaft 10 operatively connected todrive a right and left track powering or steer-drive output shaft 12 and14 by a hydrodynamic torque converter 16, a multispeed forward andreverse planetary gear range unit 18 and a right and left steerplanetary gear unit20 and 22 with a. variable ratio hydrostatic steerunit 24 provided for effecting steer bias. All of these components aresuitably supported in a housing 25 with the axes of the input shaft 10and converter 16 arranged to extend longitudinally of the vehicle andthe central axes of the components 12, 14, 18, 20, 22 and 24 arranged toextend transversely of the vehicle with the output shafts l2 and 14axially aligned.

The transmission input shaft 10 is connected by an input drive cover 26to pump blading 28 (P). The pump blading 28 exits to turbine blading 29(T) which is connected by a hub 30 to a turbine or converter outputshaft 31. Fluid is circulated toroidally in the converter and, as itleaves the turbine blading, it is redirected to the pump blading bystator blading 32 (S) that is grounded by a one-way brake 34 to thetransmission housing 25. The converter is a three element converter ofconventional design and provides torque multiplicationin theconventional manner. The converter also has a lockup clutch 35 which,when engaged, provides direct mechanical drive from input shaft 10 toconverter output shaft 31 bypassing the converters hydraulic power path.

The converter output shaft 31 delivers power to both the propulsion andsteer portions of the transmission arrangement and for this purpose isconnected to a 'bevel gear 36. Gear 36 meshes with a second bevel gear38 which is connected to the left end of a transversely arranged shaft39. A spur gear 40 connected to the right end of shaft 39 meshes with aspur gear 41 from which power is delivered by a shaft 42 to thehydrostatic steer unit 24 and is also delivered via additional gearingto the range unit 18.

In the drive to range unit 18, gear 41 meshes a schematically shown witha spur gear 44 that is connected to a drum 46. Drum 46 may be connectedby engagement of a clutch 48 to a shaft 49 and may also be connected byengagement of a clutch 50 to a sleeve shaft 51 through which shaft 49extends. The shaft 51 may be braked by engagement of a brake 52. In theplanetary gearing of range unit 18 there are three planetary gear sets54, 56 and 58. In gear set 54, a sun gear 59 is connected to the leftend of shaft 49 and meshes with pinions 60 which are carried by acarrier 61. Carrier 61 is connected to a shaft 62 that transmits theoutput from the range unit 18. Pinions 60 also mesh with a ring gear 64that may be braked by engagement of a brake 66. In gear set 56, a sungear 68 is connected to the left end of sleeve shaft 51 and meshes withpinions 69 which are carried by a carrier 70 that is connected tocarrier 61 of gear set 54 and thus to the range unit output shaft 62.Pinions 69 also mesh with a ring gear 71 which is connected to shaft 49.The shaft 51 is connected to a sun gear 72 in gear set 58. Sun gear 72meshes with pinions 74 which are carried by a carrier 76 that may bebraked by engagement of a brake 78. Pinions 74 also mesh with a ringgear 79 which is connected to carriers 61 and 70 of gear sets 54 and 56,respectively, and thus to the range unit output shaft 62.

7 Output from range unit 18 is delivered to both the steer units 20 and22. For this drive, a spur gear 80 is connected to the range unit outputshaft 62 and meshes with a spur gear 81 that is connected to across-shaft 82 that is axially aligned with the two transmission outputshafts 12 and 14. The cross-shaft 82 is connected at its right end toring gear 84 of the right steer unit 20. Ring gear 84 meshes withpinions 86 which are carried by a carrier 88 that is connected to theright output shaft 12. A right vehicle brake 89 is connected to brakeright output shaft 12. Similarly, the left end of cross-shaft 82 isconnected to ring gear 90 of the left steer unit 22.

Ring gear 90 meshes with pinions 91 which are carried by a carrier 92that is connected to the left output shaft 14. A left vehicle brake 94is connected to brake the left output shaft 14. Sun gear 96 meshing withpinions 86 of the right steer unit and sun gear 98 meshing with pinions91 of the left steer unit are connected by a direction reversing geartrain. This gear train has at its right end an annular spur gear 99which is located about cross-shaft 82, is connected to sun gear 96 ofthe right steer unit and is in mesh as schematically shown with an idlerspur gear 100 which is mounted for free rotation about shaft 39. Idlergear 100 meshes as schematically shown with a spur gear 101 which isconnected to the right end of a shaft 102. A spur gear 104 connected toshaft 102 near the shafts left end meshes as schematically shown with anannular spur gear 106 which is located about cross-shaft 82 and isconnected to sun gear 98 in the left steer unit.

Steering is made available in the transmission arrangement by thehydrostatic sheer unit 24 which is converter turbine driven by the shaft42 and is connected to drive the direction reversing gear train betweenthe sun gears 96 and 98. In this steer drive portion of the transmissionarrangement, the shaft 42 is connected to drive pump 108 of thehydrostatic steer unit 24, the pump 108 being hydraulically connected tothe axially aligned hydrostatic motor 109 of this unit. The steer motor109 is connected by a shaft 110 to a spur gear 1 11 which meshes with aspur gear 112 that is connected to the left end of shaft 102. Both thepump 108 and motor 109 are of conventional design with the pump having avariable displacement and the motor having either a variable or fixeddisplacement with speed and direction of the motor output beingcontrolled by any suitable conventional pump displacement controlmechanism as described in more detail later.

The drive producing clutches and brakes are conventional frictiondriveestablishing devices of the friction plate type each having a suitablefluid motor with a piston which is operated by fluid pressure to effectengagement of the device. Each of these devices also has suitableretraction spring means, not shown, that operate with exhaust of thefluid pressure to return the piston to its release position. The outputbrakes 89 and 94 have conventional structure of the friction plate typeand are hydraulically and manually operated simultaneously byconventional linkage which includes a rotary or otherwise movable membersuch as shaft- 114 shown in FIG. 3 which shaft turns during engagementand disengagement of these brakes.

Transmission Arrangement Operation The transmission drive trainarrangement may be operated to provide four forward speed range drives,two reverse speed range drives and hydrostatically controlled steering.For neutral, all of the drive establishing devices are disengaged todisconnect all power flow paths from the output shafts 12 and 14. Inaddition, the hydrostatic steer unit is conditioned so as not to deliverpower therethrough.-

Steering is availablein neutral by conditioning the hydrostatic steerunit 24 by its displacement control to drive the steer motor outputshaft 110 in either direction thereby causing one of the sun gears 96and 98 in the steer units to be driven in one direction and the othersun gear to be driven in the opposite direction at the same speed. Sincethe ring gears 84 and 90 are connected, they provide reaction resultingin the output shafts l2 and 14 being driven at the same speed but inopposite directions to provide a pivot steer about the vehicles centerwith the direction of vehicle turning determined by the hydrostaticmotor output direction. In the following operational description of thetransmission drive train arrangement, the hydrostatic steer unit 24 maybe considered as conditioned so that it delivers no output to the steerunits 20 and 22 so that they are free of the steer drive. Thedescription of steering operation that is available in the forward andreverse drives will follow that of the forward and reverse driveoperation. r

The first and lowest speed range forward drive is established byengaging the clutch 48 and brake 66 while all of the other driveestablishing devices are disengaged. With power to the input shaft 10,the converter 16 drives the converter output shaft 31 and this drive istransmitted through the engaged clutch 48 to sun gear 59 of gear set 54.With brake 66 engaged, the ring gear 64 of gear set 54 is held toprovide reaction to effect a simple planetary reduction drive by gearset 54 to drive shaft 62 and thus the ring gears 84 and90 of the steerunits. The sun gears 96 and 98 of the steer units by their gearedconnection provide reaction causing the carriers 88 and 92 and thusoutput shafts 12 and 14 to rotate in the same direction at a reducedspeed. The direction of rotation of the output shafts 12 and 14 thusproduced will be described as the forward direction since it producesforward vehicle motion.

To establish the second speed range forward drive, the brake 66 isdisengaged while the brake 78 is engaged to hold carrier 76 of gear set58 and clutch 48 remains engaged toprovide drive to ring tear 71 of gearset 56. This effects a compound planetary reduction drive by the gearsets 56 and 58 to drive shaft 62 and thus output shafts 12 and 14 in aspeed range higher than that provided in the first speed range forwarddrive.

To establish the third speed range forward drive, the brake 78 isdisengaged while the brake 52 is engaged to hold sun gear 68 of gear set56 and clutch 48 remains engaged to maintain drive to ring gear 71 ofthis gear set. This effects a planetary reduction drive by gear set 56to drive shaft 62 and thus output shafts l2 and 14 in a speed rangehigher than that provided in the second speed range forward drive.

To establish the fourth speed range forward drive, the brake 52 isdisengaged while the clutch 50 is engaged to provide drive to sun gear68 of gear set 56 and clutch 48 remains engaged to maintain drive toring gear 71 of this gear set. This locks up gear set 56 to provide adirect drive through the range unit to shaft 62 to drive output shafts12 and 14 in a speed range higher than that provided in the third speedrange forward drive.

To establish the first and lowest speed range reverse drive, clutch 50isengaged to drive sun gear 68 of gear set 56 and brake 66 is engaged tohold ring gear 64 of gear set 56. This effects a compound planetaryreduction drive by gear sets 54 and 56 to drive shaft 62 and thus outputshafts 12 and 14 in the reverse direction.

To establish the second speed range reverse drive, the brake 66 isdisengaged while the brake 78 is engaged to hold carrier 76 of gear set58 and clutch 50 remains engaged to provide drive to sun gear 72 of thisgear set. This establishes a simple planetary reduction drive by gearset 58 to drive shaft 62 and thus output shafts l2 and 14 in the reversedirection in a speed range higher than that provided in the first speedrange reverse drive.

Describing now the steering operation. that is available, steering ofthe differential type is available in all of the forward and reversedrives by control of the hydrostatic steer unit 24 to drive the motoroutput shaft in either direction. This drives sun gears 96 and 98 of thesteer units in opposite directions at the same speed to deliver anadditive speed component to one of the transmission output shafts 12 and14 while subtracting the same amount of speed from the other outputshaft. The resulting speed differential between output shafts 12 and 14effects turning of the vehicle with the direction of the turn determinedby the hydrostatic motor output direction.

CONTROL SYSTEM The control system for this track-laying vehicletransmission arrangement and according to the present invention,provides for automatic selection of the four forward drives and manualselection of the three lowest speed range forward drives and also thetwo reverse drives. Other functions of the control system includevehicle brake engagement, lubrication, cooling, charging of the torqueconverter and fluid pressure supply for the steering control.

Fluid Supply The fluid such as oil used in all of the control functionsfunctions is supplied by two gear-type positive dispump is drivinglyconnected to shaft 82 so that it is driven to supply fluid when thevehicle is moving forwardly and the engine is not running. The fluidsupplied by the output pump 121 supplements the fluid supply from theinput pump 120 during forward drive operation and is the only source ofmain pressure supply when the input pump is not operating. The outputpump 121 also provides fluid supply to cool the vehicle brakes and alsofor lubrication.

Main Pressure Regulator Valve The input pump 120 draws fluid from thetransmissions reservoir or sump via an intake line 122 and delivers thisfluid to a main line 124. The output pump 121 draws fluid from thetransmissionss reservoir via an intake line 126 and delivers the fluidvia a line 127 to a spring biased check valve 128 which is normallyclosed. The check valve 128 when opened by output pump pressure,connects the line 127 and thus pump 12] to deliver fluid to the mainline 124 for push starting, for example. The fluid delivered to mainline 124 from these pumps is passed through a filter 129 prior toflowing to all the downstream portions of the control system. The filter129 includes a filtering media 130 for filtering the fluid as it passesthrough and further includes a spring biased bypass valve 131 whichopens in the event the filter accumulates excessive foreign material toprovide a bypass passage for the fluid around the filtering media 130.

The main pressure supply for the control system is regulated in mainline 124 by a main pressure regulator valve 132 shown in FIG. 4. Themain pressure regulator valve 132 has a regulator valve element 134having lands (1, b and located in a stepped bore 135 of the systemsvalve body. The spaced lands b and c of valve element 134 have the samediameter and land a is adjacent to and has a slightly smaller diameterthan that of land b. Regulator valve element 134 is biased upward by aspring 136 which is located in a chamber 138 that is exhausted byexhaust port 139. The main line 124 is always connected to the bore 135in the space between lands b and c. This space is in turn alwaysconnected to a passage 141 in regulator valve element 134 which passagehas a spring loaded check valve 142 therein permitting fluid flow fromthe main line 124 to a chamber 144 at the closed upper end of valve bore135. The main line 124 is also connected through a flow restriction 146to the chamber 144. The pressure of the fluid admitted to chamber 144from main line 124 acts on the exposed end area of land a to urge thevalve element 134 downward to connect the main line 124 between lands band c first to a hydrostatic supercharge supply line 148 and then to anexhaust port 149 on further movement in the event of excessive pressuresurge. The downward movement of the valve element 134 is limited by asleeve 151. Thus, the valve 132 regulates the pressure in main line 124according to the bias provided by spring 136 with the check valve 142 incooperation with the flow restriction 146 controlling and damping theaction of the regulator valve.

The main pressure which is used to operate the converter lockup clutch35 as described in more detail later is decreased during converterlockup operation, such pressure decrease being permissible since lowtorque at higher rotating speeds is being transmitted through thetransmission. The decrease in regulated main line pressure is providedby a chamber 152 which exposes the differential area between lands a andb of regulator valve element 134. When fluid pressure indicatingconverter lockup clutch operation is delivered to chamber 152 asdescribed in more detail later, such pressure acts downward on theunbalanced area of land b of the regulator valve element 134 to decreasemain line pressure.

Secondary Main Pressure Regulator Valve Main line 124 is also connectedto a secondary main pressure regulator valve 154 which is shown in FIG.4. Valve 154 has a regulator valve element 156 having spaced lands a andb of equal diameter located in a bore 158 in the valve body. The valveelement 156 is biased to an open position as shown by a spring 159. Asecondary main line 161 is always connected between lands a and b to apassage 162 in the valve element 156 which passage has a spring loadedcheck valve 164 .therein permitting flow from the secondary main line161 to a chamber 166. Chamber 166 is at the closed upper end of bore 158and exposes the end area of land a. The secondary main line 161 is alsoconnected through a flow restriction 168 to chamber 166. The pressure ofthe fluid in chamber 166 acts downward on the end of land a to bias thevalve element 156 downward against the bias of spring 159 to close theconnection between the secondary main line 161 and the main line 124 andthus the valve regulates the pressure in the secondary main line 161 inaccordance with the spring bias with the check valve 164 in cooperationwith the flow restriction 168 controlling and damping the regulatoraction. Since the valve 154 is thus a downstream regulator valve, thepressure in the secondary main line 161 will not fluctuate when thepressure in main line 124 fluctuates.

Supercharge Pressure Regulator Valve The pressure of the fluid in thehydrostatic supercharge supply line 148 which is fed with the overagefrom the main pressure regulator valve 132 as described previously isregulated by a supercharge pressure regulator valve 169. The superchargepressure regulator valve 169 operates on the pressure in line 148 toprovide a regulated supply pressure for the hydrostatic steer unit 24.The valve 169 has a regulator valve element 171 which has spaced lands aand b of equal diameter located in a bore 172 of the valve body and isbiased upward by a spring 174. The line 148 is always connected to thespace between lands a and b and this space is always connected to apassage 176 in the valve element which passage has a spring loaded checkvalve 178 therein permitting fluid flow from line 148 to a chamber 179at the closed upper end of valve bore 172.

The space between lands a and b is also always connected through a line181 having a flow restriction 182 therein to chamber 179. The pressureof fluid admitted to chamber 179 acts on the end of land a against thebias of spring 174 to urge valve element 171 downward to connect line148 between lands a and b first to a converter supply line 184 and thento an exhaust port 186 in the event there is excessive pressure surge.Downward movement of valve element 171 is limited by a sleeve 187. Thus,the pressure of the fluid in the hydrostatic supercharge supply line 148is regulated according to the bias of spring 174 with the check valve178 and flow restriction 182 cooperating to control and dampen theregulator action.

The fluid in the hydrostatic supercharge supply line 148 is used tosupply the hydrostatic steer unit 24. The hydrostatic steer unit controlsystem may be of the type disclosed in US. Pat. application Ser. No.779,502, now US. Pat. No. 3,640,157 filed Nov. 27, 1968, and entitledPower Train Control System by Robert H. Schaefer. Reference may be madeto the aforementioned Schaefer patent application for further details onthe hydro-static steer drive control.

Converter Relief Valve land b located in a stepped bore 191 in the valvebody.

A spring 192 located in the closed upper end of valve bore 191 biasesvalve element 189 downward to the position shown which is determined bythe lower shoulder of land b abutting the step in the valve bore. Thelower end of bore 191 is closed to provide chamber 201 which isconnected to the converter supply line 184 and with fluid admitted tochamber 201, the pressure of this fluid acts upward on valve element189. When the pressure bias on valve element 189 exceeds the bias ofspring 192 the valve element 189 is moved upward to connect chamber 201to a converter bypass line 202 which delivers fluid for lubrication orto cool the brakes as described in more detail later. Thus, the pressurein the converter supply line 184 cannot exceed a value determined by thebias of spring 192. A chamber 204 exposes the differential area betweenlands a and b of valve element 189. When fluid pressure indicatingconverter clutch lockup operation is delivered to chamber 204 asdescribed in more detail later, such pressure acts upward on theunbalanced area of land b to urge valve element 189 upward against thebias of spring 192 thereby reducing the effective downward bias on valveelement 189 and thus reducing the pressure in the converter supply line184. Anexhaust port 205 exhausts the closed upper end of bore 191. Theconverter supply line 184 is connected to supply fluid to the torqueconverter 16 as shown in FIG. 2 with the fluid being directed from theconverter to the systems reservoir via a converter return line 207.

Push Start-Diverter Valve A push start-diverter valve 208 shown in FIG.3 operates to divert fluid from the output pump 121 to cool the outputbrakes 89 and 94. The valve 208 comprises a spool valve element 209having spaced lands a and b of equal diameter located in a bore 212 inthe valve body. spring 222 normally holds valve element 209 in a pushstart position as shown in which the output pump delivery line 127 isblocked from the converter return line 207 by land b while theline 127is open between lands a and b to deliver fluid to the main line 124 viathe check valve 128. The upper end of bore 212 is closed to provide achamber 224 which is connected to the hydrostatic supercharge supplyline 148 through a flow restriction 225. When hydrostatic superchargepressure is at its normal regulated value, this pressure acting inchamber 224 on the upper end of valve element 209 is effective to movethis valve element downward to a divert position in which the outputpump delivery line 127 is connected between lands a and b to theconverter return line 207. When main pressure is made available to achamber 226 as described in more detail later, the fluid pressure actingin this chamber acts upward on valve element 209 and thus assists thespring 222 in holding the valve element 209 in its push start positionBrake Apply Valve A brake apply valve 228 shown in FIG. 3 controls theengagement of the output brakes 89 and 94 and comprises a spool valveelement 229 having spaced lands a and b of equal diameter located in avalve bore 231. The brake-apply valve further comprises a spool valveelement 232 having spaced lands a and b of equal diameter located in anenlarged diameter portion 234 of bore 231, the lands on valve element232 being larger in diameter than the lands on valve element 229. Aspring 236 biases valve element 229 leftward while a regulator spring238 located between the valve elements 229 and 232 urges the valveelements apart with such movement being limited by a rod 239. A lever240 is connected to the brake linkage shaft 114 and thus pivots when theoutput brakes are applied on clockwise rotation of shaft 114. Lever 240is engageable with a stop 241 in a brake release position as shown andhas a pin 242 which engages an annular channel 244 near the left end ofvalve element 232 where it extends out of the large diameter boreportion 234. When the lever 240 is against stop 24]., the valve elements232 and 229 are positioned as shown with land b of valve element 229blocking a branch of the main line 124 at the bore 231 while an exhaustport 246 is connected between lands a and b of valve element 229 to avehicle brake feed line 248. The vehicle brake feed line 248 is connected to fluid pressure operated motors 249 and 250 which operate theoutput brakes 94 and 89, respectively. Also in the brake releaseposition, the land b of valve element 232 blocks another branch of themain line 124 while a coolant signal line 252 is connected between landsa and b of this valve element to exhaust through the left end of thelarge diameter bore portion 234.

When the brake linkage shaft 114 and thus lever 240 are rotatedclockwise as viewed in FIG. 3, the bias of spring 236 is sufficientlylarge enough to hold valve element 229 in position while valve element232 moves rightward relative to the valve element 229 to connect themain line 124 between lands a and b to the coolant signal line 252. Thenon continued brake apply movement, the rightward pushing force overcomesthe bias of spring 236 to effect rightward movement of the valve element229 so that its land a then blocks the exhaust port 246 while the mainline 124 is then connected between lands a and b of this valve elementto the vehicle brake feed line 248 to hydraulically engage the outputbrakes. The brake feed line 248 is connected between lands a and b ofvalve element 229 via ports 253 to a chamber 254. The pressure inchamber 254 acts leftward on valve element 229 against the bias ofregulator spring 238 to effect regulation of the brake apply pressure.The force applied by spring 238 is proportional to brake lever movementand thus thebrake apply pressure is proportional to brake leverposition.

Brake Coolant Valve A brake coolant valve 255 controls the supply offluid to cool the output brakes 94 and 89 as these position by a piston265 which is located in a bore 266.

and is fixed to pin 258. Piston 265 is moved downward on supply of fluidpressure to a chamber 267 which is supplied with pressure by the coolantsignal line 252 from the brake apply valve 228. The line 202 from theconverter relief valve 188 isconnected to chamber 262. In addition theconverter return line 207 is connected through a cooler 269 to thechamber 262. When the brake coolant valve 255 is closed, the fluid thussupplied to chamber 262 is delivered to a lubrication supply line 270which supplies fluid to lubricate the various parts of the transmission.The pressure of the fluid being thus delivered for lubrication islimited by a spring biased poppet type valve 271 which exhausts fluidoverage to an exhaust port 272. A small portion of the fluid supplied tochamber 262 is delivered by a flow restriction 273 to chamber 264 whichis connected by coolant feed lines 274 and 275 to deliver fluid to thefriction surfaces of the output brakes 89 and 94, respectively. Thissmall amount of fluid delivery when the output brakes are disengaged isto provide lubrication of these brakes moving parts. Alternatively, whenthe brake apply valve 228 is operated to engage the brakes whereby fluidpressure is made available to chamber 267 on initial brake demand, thevalve element 256 is moved downward by piston 265 to its open positionto provide unrestricted flow communication between chambers 262 and 264so that the fluid overage in line 202 from the converter relief valve188 and the fluid in the converter return line 207 is made Governors Thecontrol system has two governors providing separate speed governedpressures. These pressures are used to control different operations inthe control system. One governor 278 which is of the fluid velocity typeand will be called the G1 governor is shown in FIG. 2 and has an annulartrough 279 that is connected to rotate with the converter turbine 29.The trough 279 is supplied with fluid from any suitable line such asfrom the secondary main line 161. The fluid rotating with trough 279impinges on the open end of a stationary Pitot tube 281 to provide in aG1 line 282 a governor pressure which is proportional to converterturbine speed and will be called G1 pressure.

The other governor 284, which will be called the G2 governor, is shownin FIG. 6. The G2 governor is of a conventional type and is suppliedwith fluid from the secondary main line 161.-The G2 governor 284 may,for example, be of the mechanical type disclosed in US. Pat. No.2,762,384 issued to M. S. Rosenberger. The G2 governor 284 is driven ata speed proportional to that of the output shafts l2 and 14 to providein a G2 line 289 a governor pressure which is proportional to vehiclespeed.

Throttle Pressure Regulator Valve A pressure indicating engine torquedemand which is used for control of automatic shifting is provided by athrottle pressure regulator valve 291 which is shown in FIG. 4. Valve291 which may also be called a T.V. valve comprises a regulator valveelement 292 of the spool type having spaced lands a and b of equaldiameter located in a small diameter portion of a stepped bore 294 inthe valve body. The valve also has a control valve element 296 locatedin a large diameter portion of bore 294 and a spring 298 which islocated between elements 292 and 296 to urge them apart.

The positioning of the control valve element 296 is controlled by alever 299 which contacts the projecting upper end of this valve elementand is pivoted by a pivot pin 300 on the valve body, the lever 299 beingconnected by suitable linkage to the engine throttle control, not shown,which controls the throttling of the vehicles engine powering thetransmission. When the engine throttle is in its zero throttle position,the opposite end 301 of lever 299 is against a stop 302 with the valveelements 292 and 296 at their maximum distance apart. At this zeroengine throttle position, there is a spring loading on theregulator'valve element 292 so that the secondary main line 161 isconnected between lands a and b to a T.V. line 304 to establish aminimum T .V. pressure to position pilot valves as described in moredetail later.

The T.V. line 304 is continuously connected to the space between lands aand b of the regulator valve element 292 and this space is connected toa passage 306 in the valve element having a spring loaded check valve308 therein to permit flow from the T.V. line 304 to a chamber 309 atthe closed lower end of the valve bore. The T.V. line 304 is alsoconnected to chamber 309 through a flow restriction 311. The fluidpressure in chamber 309 urges valve element 292 upward to close offsecondary main line 161 and thus the valve regulates to provide in theT.V. line 304 a pressure proportional to the acting spring bias of thespring 298. As the engine throttle is opened, the lever 299 is pivotedclockwise moving the control valve element 296 downward. This downwardmovement causes the spring 298 to provide a progressively increasingdownward regulating bias and the pressure of the fluid delivered betweenlands a and b of regulator valve element to the T.V. line 304 increasesaccordingly. Since movement of the control valve element 296 isproportional to the engine throttle opening which is indicative ofengine torque demand, the pressure in T.V. line 304 which will be calledT.V. pressure is also proportional to engine throttle opening andindicative of engine torque demand. Thus the T.V. pressure produced .inT.V. line 304 is proportional to engine throttle opening and increaseswith increasing throttle opening and torque demand.

Neutral Valve The main line 124 is connected to a neutral valve 312shown in FIG. 6 which operates to condition the transmission in neutral.The neutral valve 312 comprises a spool valve element 314 having spacedlands a, b and c of equal diameter located in a bore 316 of the valvebody. A spring 317 which is located in a chamber 318 at the upper end ofvalve bore 316 normally urges the valve element 314 downward to theposition shown which will be called the neutral position. In the neutralposition, a range main line 319 which supplies main line pressure forengaging the different drives is connected between lands b and c to anexhaust port 321 while the main line 124 is connected between lands aand b to a signal line 322 which has a flow restriction 324 therein andis connected to chamber 318. A solenoid valve 325 is connected to line322 between the flow restriction 324 and chamber 318 and whendeenergized, is spring biased to close an exhaust port 326 so thatpressure in chamber 318 builds tofull main line pressure to assistspring 317 in holding the neutral valve in its neutral position. Whensolenoid valve 325 is energized, it opens the port 326 so that pressureis prevented from building in chamber 318 while the flow restriction 324maintains the main line pressure upstream thereof. The secondary mainline 161 is connected through a flow restriction 327 to a chamber 328 atthe lower end of bore 316 so that secondary main pressure is availableto urge the valve element 314 upward against the downward bias discussedabove. A solenoid valve 329 is connected to secondary main line 161between flow restriction 327 and chamber 328 and when deenergized, isspring biased to close an exhaust gized. A manually movable pin 332engageable with the lower end of valve element 314 is provided so thatthe vehicle operator can manually move the neutral valve 312 to itsdrive position where there is electrical power interruption.

3-4 Shift Valve The range main line 319 is connected to a 3-4 shiftvalve 333 shown in FIG. which provides for shifting between the thirdand fourth forward drives. The 3-4 shift valve 333 comprises a spoolvalve element 334 having spaced lands a, b and c of equal diameterlocated in a bore 335 of the valve body. A spring 337 is port 330 sothat pressure in chamber 328 builds to full secondary main pressure. Theupward bias provided by secondary main pressure is effective to move thevalve element upward to a drive position only against the bias of spring317 and thus is effective to move the valve element 314 to thedrive-position only when the solenoid valve 325 is energized to exhaustthe chamber 318. In the drive position, the main line 124 is connectedto the range main line 319 between lands b and c of valve element 314while the signal line 322 is connected between lands a and b to anexhaust port 331. When solenoid valve 329 is energized, it opens theport 330 so that pressure is prevented from building in chamber 328while the flow restriction 327 maintains the secondary main pressureupstream thereof. Thus, when solenoid valve 329 is energized the neutralvalve 312 will be moved from its drive position to its neutral positionand be maintained in the latter position by either the bias of spring317 or this spring bias plus the located in a chamber 338 which iscontinuously exhausted by a port 339 normally urges the valve element334 upward to an upshift position as shown in which it connects therange main line 319 between lands b and c to a 2-3 shift valve feed line341 while connecting an exhaust port 342 between lands a and b to a line.344 which is for transmitting fluid to operate the clutch 50 asdescribed in more detail later. The 3-4 shift valve element 334 is moveddownward against the spring bias to a downshift position upon deliveryof sufficient fluid pressure to a chamber 346 at the closed upper end ofvalve bore 336, the supply of fluid pressure to chamber 346 beingdescribed in more detail later. The 3-4 shift valve 333 is the downshiftposition connects the range main line 319 between the lands a and b tothe line 344 while the 2-3 shift valve feed line 341 is connectedbetween lands b and c to an exhaust port 347.

2-3 Shift Valve The 2-3 shift valve feed line 341 is connected to a 2-3shift valve 348 shown in FIG. 5 which controls the shifting between thesecond and third forward drives. The 2-3 shift valve 348 comprises aspool valve element 349 having spaced lands a, b and c of equal diameterlocated in a bore 351 in the valve body. A spring 352 located in achamber 354 at the closed lower end of bore 351, which chamber isexhausted by an exhaust port 355, biases the valve element 349 upward toan upshift position as shown in which it connects the 2-3 shift valvefeed line 341 between lands b and c to a line 356. Line 356 is connectedto a fluid pressure operated motor 357 that operates the brake 52 asshown in FIG. 2. in the upshift position, the b 2-3 shift valve 348 alsoconnects an exhaust port 358 between lands a and b to a line 349 that isconnected to chamber 226 of the push start-diverter valve 208 and isalso connected to transmit fluid to operate the clutch 50 as describedin more detail later. The valve element 349 is urged downward againstthe bias of spring 352 to a downshift position upon delivery ofsufficient fluid pressure to a chamber 361 at the: closed upper end ofbore 351, this fluid pressure delivery being described in more detaillater. In the downshift position, the 2-3 shift valve feed line 341 isconnected between lands a and b to the line 359 while the line 356 isconnected between lands b and c to an exhaust port 362.

1-2 Shift Valve The l-2 shift valve feed line 359 is connected to a l-2shift valve 364 which is shown in FIG. 5 and provides for shiftingbetween the first and second forward drives in both forward and reverse.The l-2 shift valve 364 comprises a spool valve element 366 havingspaced lands a, b and c of equal diameter located in a bore 367 of thevalve body. The valve element 366 is normally biased upward to anupshift position as shown by a spring 368 that is located in a chamber369 at the closed lower end of bore 367 which is connected to an exhaustport 371. In the upshift position, the I-2 shift valve feed line 359 isconnected between lands b and c to a line 372 which is connected to afluid pressure operated motor 374 which operates the brake 78 as shownin FIG. 2. In the upshift position, the shift valve element 366 alsoconnects an exhaust port 376 between lands a and b to a line 378 whichis connected to a fluid pressure operated motor 379 that operates thebrake 66. The valve element 366 is urged downward against the bias ofspring 368 to a downshift position upon sufficient pressure buildup in achamber 381 at the closed upper end of valvebore 367, the supply offluid to chamber 381 being described in detail later. Pressure buildupin chamber 381 is controlled by a solenoid valve 382 which whendeenergized is spring biased to close an exhaust port 383' to permitpressure buildup in chamber 381 to effect downward movement of valveelement 366 to its downshift position. Alternatively, energization ofsolenoid valve 382 opens port 383 so that pressure cannot build inchamber 381 to bias valve element 366 to its downshift position. In thedownshift position, the line 372 is connected between lands b and c toan exhaust port 384 while the l-2 shift valve feed line 359 is connectedbetween lands a and b to the line 378.

3-4 Pilot Valve A 3-4 pilot valve 386 shown in FIG. 5 controls theoperation of the 3-4, shift valve 333 and comprises a spool valveelement 387 having spaced lands a and b located in a bore 388 in thevalve body. A governor plug 389 and a T.V. plug 391 are located in largediameter portions of bore 388 at opposite ends if the valve element 387and are exposed at their outermost ends to a governor chamber 392 and aT.V. chamber 394, respectively. The governor chamber 392 is connected tothe G2 governor line 289 and the T.V. chamber 394 is connected to theT.V. line 304. When the downward bias on this valve train provided byT.V. pressure acting in T.V. chamber 394 exceeds the oppositely actingbias provided by G2 pressure acting in governor chamber 392 the 3-4pilot valve train is biased to a downshift demand position as shown. Inthe downshift demand position, an exhaust port 396 is connected betweenlands a and b to a 3-4 shift valve signal line 397 which is connected tochamber 346 of the 3-4 shift valve 333. Alternatively, when the governorpressure bias exceeds the T.V. pressure bias, the 3-4 pilot valve trainis moved to an upshift demand position in which the secondary main line161 is connected between lands a and b to the 3-4 shift valve signalline 397 while exhaust port 396 is blocked by land b. An exhaust port398 is provided to exhaust leakage. A chamber 399 is connected to amanual signalline 401 and on delivery of sufficient fluid pressurethereto,

there is provided a fluid pressure bias that operates on the full upperend area of land a to hold the valve element 387 in its downshift demandposition, the supply of fluid pressure to line 401 and thus to chamber399 being described in detail later. The lands a and b of valve element387 have slightly different diameters and the bore 388 is steppedaccordingly to provide a hysteresis effect that prevents valve huntingand results in a downshift speed slightly lower than the upshift speed.

2-3 Pilot Valve The secondary main line 161 is also connected to a 2-3pilot valve 402 shown in FIG. 5 which controls the 2-3 shift valve 348.The 2-3 pilot valve 402 comprises a spool valve element 404 havingspaced lands a, b and cv located in a bore 406 of the valve body. Agovernor plug 407 and a T.V. plug 408 are located at opposite ends ofthe valve element 404 in enlarged diameter portions of bore 406. Theplugs 407 and 408 are exposed at their outermost ends to a governorchamber 409 and a T.V. chamber 411 which are connected to the G2governor line 289 and T.V. line 304, respectively. When the downwardbias provided by T.V. pressure acting in chamber 411 on the T.V. plug408 exceeds the oppositely acting bias provided by governor pressureacting upward on the governor plug 407, the 2-3 pilot valve train isheld in a downshift demand position as shown in which the secondary mainline 161 downstream of a flow restriction 414 is blocked from an exhaustport 416 by land c. The secondary main line 161 is connected downstreamof flow restriction 414 to chamber 361 of the 2-3 shift valve 348 andthus pressure is permitted to build in chamber 361 when the 2-3 pilotvalve 402 is in its downshift demand position. A]- ternatively, when thegovernor pressure bias exceeds the T.V. pressure bias, the 2-3 pilotvalve train arrangement is moved to an upshift demand position in whichthe secondary main line 161 downstream of flow restriction 414 isconnected between lands b and c to the exhaust port 416 to thus preventpressure buildup in chamber 361 of the 2-3 shift valve 348 while flowrestriction 414 maintains secondary main pressure upstream thereof. Anexhaust port 417 is provided to exhaust leakage. A chamber 419 which isconnected to manual line 401 provides for effecting a fluid pressurebias that acts on the full end area of land a to hold the valve element404 in its downshift demand position.

Further regarding the control of chamber 361 of the 2-3 shift valve 348,there is provided a solenoid valve 420 which when deenergized, is springbiased to close an exhaust port 421 in secondary main line 161downstream of the flow restriction 414. Thus, when solenoid valve 420 isdeenergized, pressure is permitted to build in chamber 361 of the 2-3shift valve 348 when the 2-3 pilot valve 402 is in its downshift demandposition. Alternatively, when the solenoid valve 420 is energized, theexhaust port 421 is opened to prevent pressure buildup in chamber 361 ofthe 2-3 shift valve 348. The lands a and b of valve element 404 haveslightly differentdiameters and lands b and c have the same diameter andthe bore 406 is stepped accordingly to provide a hysteresis effect thatprevents valve hunting and results in a downshift speed slightly lowerthan the upshift speed.

1-2 Pilot Valve The secondary main line 161 is also connected to a 1-2pilot valve 422 which is shown in FIG. and controls the operation of theI-2 shift valve 364. The 1-2 pilot valve 422 comprises a spool valveelement 424 having spaced lands a, b and c located in a bore 426 of thevalve body. A governor plug 428 and a plug 429 are located at theopposite ends of valve element 424 in accommodating portions of bore426. A chamber 431 exposing the outermost end of the governor plug 428is connected to the G2 governor line 289. A T.V. chamber 432 exposingthe upper end of land a of the valve element 424 is connected to theT.V. line 304. A third chamber 433 exposing the upper end of plug 429 isconnected to manual signal line 401. When the downward bias on valveelement 424 provided by T.V. pressure acting in chamber 432 on the endof land a exceeds the oppositely acting bias provided by G2 pressureacting in chamber 431 on the end of governor plug 428, the l-2 pilotvalve train arrangement is held in a downshift demand position as shown.In the downshift demand position, the secondary main line 161 downstreamof a flow restriction 436 is blocked from an exhaust port 438. Anexhaust port 439 is for exhausting any leakage. The secondary main line161 downstream of flow restriction 436 is also connected to chamber 381of the l-2 shift valve 364 and thus pres sure may build to bias the l-2shift valve to its downshift position. Alternatively, when the governorpressure bias exceeds the T.V. pressure bias, the l-2 pilot valve trainis moved upward to an upshift demand .position in which the secondarymain line 161 downstream of the flow restriction 436 is connectedbetween lands b and c to the exhaust port 438. When pressure isdelivered from manual signal line 401 to chamber 433, the pressure inthis chamber acts downward on plug 429 to hold the valve element 424 inits downshift demand position. The lands a and b of. valve element 424have slightly different diameters and lands b and c have the samediameter and the bore 426 is stepped accordingly to provide a hysteresiseffect that prevents valve hunting and results in a downshift speedslightly lower than the upshift speed.

Manual Select Valve The secondary main line 161 is also connected to amanual select valve 441 which is shown in FIG. 5 and provides forrnanualselection of the first, second and third forward drives. Themanual valve 441 comprises a spool valve element 442 having spaced landsa and b of equal diameter located in a bore 444 in the valve body. Aspring 446 which is located in a chamber 447 that is exhausted by anexhaust port 448 biases the valve element 442 downward to the positionshown which will be called the manual select position. In thisposition,.

the secondary main line 161 is connected between lands a and b to themanual signal line 401 which is connected to the chambers 399, 419 and433 of the 3-4, 2-3 and 1-2 pilot valves 38,6, 402 and 422,respectively. A chamber 451 at the closed lower end of bore 444 isconnected through a flow restriction 454 to the secondary main line 161.A solenoid valve 455 when deenergized is spring biased to close anexhaust port 456 provided in the secondary main line 161 between theflow restriction 454 and chamber 451 to thus permit pressure buildup inthe chamber 451. On such pressure buildup, the valve element442 is movedupward against the bias of spring 446 to a manual shut-off position toconnect the manual signal line 401 between lands a and b to an exhaustport 458 while the secondary main line 161 is blocked by land b.Alternatively, when the solenoid valve 455 is energized, it opens theexhaust port 456 to prevent pressure buildup in chamber 451 to permitthe spring 446 to return the valve element 442 to its manual selectposition.

Directional Valve A directional valve 461 shown in FIG. 6 controlswhether a forward or reverse drive is engaged and thus determines thedirection of vehicle travel. Valve 461 comprises a spool valve element462 having spaced lands a, b, c and d of equal diameter located in abore 464 of the valve body. A plug 465 is also located in bore 464 abovevalve element 462. A spring 466 located in a chamber 468 at the closedlower end of bore 464 urges valve element 462 and plug 465 upward to aforward drive position as shown. In the forward drive position, the mainline 124 is connected between lands c and d to a line 471 which isconnected to a fluid pressure operated motor 472 shown in FIG. 2 thatoperates the clutch 48. The directional valve in the forward driveposition also connects the line 344 from the 34 shift valve 333 to aline 474 which is connected as shown in FIG. 2 to a fluid pressureoperated motor 476 that operates the clutch 50. The directional valve461 in the forward drive position also connects an exhaust port 478betweenlands aand b to a line 479 while land b blocks the line 359 whichis ported around land 0 and is connected to both the l-2 shift valve 364and the push start-diverter valve 208. Positioning of the directionalvalve is controlled by fluid pressure supplied to the chamber 468 andalso to chambers 481 and 842 which are exposed to the upper ends ofvalve element 462 and 465, respectively. The chamber 468 is connected tothe line 471 through a flow restriction 484. A solenoid valve 485, whendeenergized, is spring biased to close an exhaust port 486 connected toline 471 between flow restriction 484 and chamber 468 to permit pressurebuildup in this chamber. Alternatively, when solenoid valve 485 isenergized, it opens the exhaust port 486 to prevent pressure buildup inchamber 468. The chamber 482 is connected by a line 488 having a flowrestriction 489 therein to receive secondary main pressure as describedin more detail later. A solenoid valve 490, when deenergized, closes anexhaust port 491 connected to line 488 between chamber 482 and flowrestriction 489 to permit pressure buildup in chamber 482.Alternatively, when solenoid valve 490 is energized, it opens theexhaust port 491 to prevent pressure buildup in chamber 482. Wheneverpressure builds in eitherchamber 481 or 482 and there is no pressurebuildup in chamber 468, the directional valve train is moved downward toa reverse drive position against the bias of spring 466. In the reversedrive position, the line 479 is then connected between lands a and b tothe line 359 which is then connected between lands b and c to the line474 that feeds fluid to engage.

Forward-Reverse Inhibitor Valve A forward-reverse inhibitor valve 494shown in FIG. 6 inhibits or prevents shifting between forward andreverse drive above a certain vehicle speed. The valve 494 comprises aspool valve element 496 having spaced lands a, b and c of equal diameterlocated in a bore 498 in the valve body. The valve element 496 is biaseddownward to a shift-permit position as shown by a spring 499 which islocated in a chamber 501 that is exhausted by an exhaust port 504. Thevalve element 496 is biased upwardto a shift-prevent or inhibit positionby G2 pressure which is delivered by connection of the G2 line 289 to achamber 506 where pressure acts upward on the lower end of valve element496. In the shift-permit position, the secondary main line 161 isconnected between lands a and b to line 488, the line 479 connected tothe directional valve 461 is blocked by land b and an exhaust port 508is connected between lands b and c to a line 509 which is connected tochamber 481 of the directional valve 461. When the governor pressurebias exceeds the spring bias, the valve element 496 is moved to theshift-inhibit position in which the line 488 is connected between landsa and b to an exhaust port 510, the secondary main line 161 is blockedby land b and the lines 479 and 509 are connected between lands b and c.A manually movable pin 51 1 engageable with the lower end of valveelement 496 is provided so that the vehicle operator can manuallycondition the forward-reverse inhibitor valve 494 in its shift-preventposition against the bias of spring 499.

Trimmer Valves Conventional trimmer valves 512, 513, 514 and 515 areconnected to the lines 378, 372, 356 and 474 which deliver fluid toengage brake 66, brake 78, brake 52 and clutch 48, respectively. Thesetrimmer valves may be of the type shown in U.S. Pat. No. 3,207,182issued to J. O. Edmunds. On supply of fluid to engage the respectivedrive establishing devices, the associated trimmer valve operates tofirst regulate the pressure of the fluid supplied at a low value andthen gradually regulates the pressure at higher values with increasingtime until full main line pressure is reached at which time the trimmervalve then ceases to operate, such trimmer valve operation providing thegradually increasing pressure for smooth drive engagement.

Priority Valve A priority valve 516 shown in FIG. 5 assures maintenanceof the drive direction during shifting when there is trimmer valveoperation and comprises a valve element 517 which is mounted in a bore518 in the valve body and is biased by a spring 519 to close a branch521 in the range main line 319 between the neutral valve 312 and all ofthe shift valves. In this closed valve position, fluid flowing throughrange main line 319 to the shift valves is required to pass through aflow restriction 522. Alternatively, when the pressure in the range mainline 319 upstream of flow restriction 522 is high enough to move thevalve element 517 downward against the bias of spring 519, the branch521 is opened permitting free fluid flow to the shift valves.

Lockup Shift Valve A lockup shift valve 524 shown in FIG. 4 controls theengagement of the converter lockup clutch 35. The

lockup shift valve 524 comprises a spool valve element 526 having spacedlands a, b and 0 located in a bore 528 of the valve body. The valve 524further includes a governor plug 529 which is located in an enlargeddiameter portion of bore 528 and is exposed at its lower end to achamber 530 which is connected to the G1 governor line 282. At the otherclosed end of bore 528 there is provided a chamber 532 which isconnected to the T.V. line 304. When the downward bias on valve element526 provided by T.V. pressure acting in chamber 532 exceeds the governorpressure bias provided by G1 governor pressure acting upward in chamber530 on governor plug 529, the lockup shift valve train is held in alockup clutch disengage position as shown. In the disengage position, anexhaust port 531 is connected between lands b and c to a line 533 whichis connected as shown in FIG. 2 to a fluid pressure operated motor 534that operates the converter lockup clutch 35. The lockup shift valve 524in the lockup disengage position also connects an exhaust port 535between lands a and b to a line 5.36 which is connected to chamber 204of the converter relief valve 188, the line 536 also being connected tochamber 152 of the main pressure regulator valve 132.

When the G1 governor pressure bias exceeds the T.V. pressure bias, thelockup shift valve 524 is moved upward to a lockup clutch engageposition in which the line 533 to the converter lockup clutch motor 534is connected between lands band c to a line 538 which supplies fluidpressure to this valve for the converter lockup clutch engagement asdescribed in more detail later. Also in the converter lockup engageposition, the secondary main line 16b is connected between lands a and bto the line 536 so that pressure is available to chamber 204 of theconverter relief valve 188 to reduce converter inlet pressure and isalso made available to chamber 152 of the main pressure regulator valve132 to reduce main line pressure. An exhaust port 549 is for exhaustingleakage. The lands a and b of valve element 526 have slightly differentdiameters and lands b and c have equal diameters with the bore 528stepped accordingly to provide a hysteresis effect to prevent valvehunting.

Lockup Timer Valves Two lockup timer valves 541 and 542 shown in MG. 4provide for momentariiy interrupting converter lockup clutch engagementduring shifting between the three highest speed range forward drives.The lockup timer valve 541 which may also be called the 2-3 and 3-2lockup timer valve since it operates on an upshift from the second tothe third forward drive and also on a downshift from the third to thesecond forward drive, comprises a cylindrical valve element 544 locatedin a bore 546 which is closed at both ends. The line 356 which transmitsfluid to operate brake 52 is connected through a flow restriction 548 tothe upper end of bore 546 and is also connected to this bore throughanother flow restriction 549 at a point spaced therealong less than thelength of the valve element 544. The line 372 which transmits fluid tooperate the brake '78 is connected through a flow restriction 551 to theopposite end of bore 546 and is also connected through anotherflow-restriction 552 to the'bore at a point spaced less than the lengthof valve element 544. The length of bore 546 in comparison to the lengthof valve element 544 is such that a line 554 is connected to the bore attwo spaced points with one point being just below the valve element 544when the valve element is in the position shown and the other point isjust above the valve element 544 when the valve element is at theopposite end of bore 546. Assuming initial fluidipressure supply to line356 while line 372 is being exhausted and with valve element 544 in theposition shown, the pressure of the fluid admitted through the flowrestriction 548 will force the valve element 544 downward toward theopposite end of bore 546. During such downward movement the valveelement 544 will open the line 356 to the bore 546 through the flowrestriction 549 to ac celerate movement and then provide for connectionof the line 356 through both of the flow restrictions 548 and 549 fornormal flow to first one branch and then both branches of the line554.'Alternatively, when the valve element 544 is in the lower positionand on initial fluid delivery to line 372 and then through flowrestriction 551 while line 356 is being exhausted,the pressure thenacting on the lower end of valve element 544 will force the valveelement upward to the position shown. During such upward movement thevalve element 544 will open the line 372 to bore 546 through flowrestriction 552 to'accelerate movement and then provide for connectionof the line 372 through both of the flow restrictions 551 and 552 fornormal flow to first one branch and then both branches of line 554.

The other lockup timer valve 542 which may be called the 3-4 and 4-3lockup timer valve because of its operation, comprises a cylindricalvalve element 556 that is located in a bore 558 in the valve body whichbore is closed at both ends. The line 344 which supplies fluid to engagethe clutch 50 is connected through a flow restriction 559 to the closedupper end of bore 558 and is also connected through another flowrestriction 561 to this bore at a point located at a distance from theclosed upper end of the bore less than the length of the valve element556. The line 554 from the lockup timer valve 541 is connected throughaflow restriction 564 to the closed lower end of bore 558 and is alsoconnected through another flow restriction 566 to this bore at a pointlocated at a distance from the closed lower end of" bore 558 less thanthe length of valve element 556. The line 538 which leads to the lockupshift valve 524 is connected to bore 558 at two spaced points with onepoint being just below valve element 556 when this valve element is inthe position shown and the other point being just above this valveelement when the valve element is at the opposite end of this bore. Whenthe valve element 556 is in the position shown and on initial fluidsupply tothe line 344 while line 554 is being exhausted, the pressure ofthe fluid supplied through flow restriction 559 to the upper end of bore558 acts on the upper end of valve element 556 to urge this valveelement downward toward the opposite end of the bore. As valve element556 moves downward, it opens line 344 to bore 558 through flowrestriction 561 to accelerate movement and then provides for connectionof the line 344 through both of the flow restrictions 559 and 561 fornormal flow to first the one branch and then both branches of line 538.Alternatively, when the valve element 556 is at the lower end of bore558 and then on initial fluid supply to line 554 while line 344 is beingexhausted, the fluid supplied through the flow restriction 564 initiatesupward movement of the valve element 556 with such movement beingaccelerated on opening of line 554 to bore 558 through the flowrestriction 556. On continued movement of valve element 556 to theposition shown, the line 554 is connected through both flow restrictions564 and 566 to one and then both branches of the line 538 which suppliesthe lockup shift: valve 524.

Operators Controls The operators controls for controlling the controlsystem comprises a bank of switches shown in FIG. 6 which are located inthe operator compartment of the vehicle remote from the power train. Asuitable DC power source 570 is connected to a power line 571 which isconnected to the input side of switches 572, 574, 575, 57.6, 578, 579and 580 which are all normally open. When switch 572 is closed, ittransmits power to line 581 that is connected to solenoid valve 490.When switch 574 is closed, it supplies power to a line 582 that isconnected to solenoid valve 485. When switch 575 is closed, it suppliespower to a line 584 that is connected to solenoid valve 325. .Whenswitch 576 is closed, it supplies power to a line 585 that is connectedto solenoid valve 329. When switch 578 is closed, it supplies power to aline 588 that is connected to solenoid valve 455. When switch 579 isclosed, it supplies power to a line 589 that is connected to solenoidvalve 420. When switch 580 is closed, it supplies power to a line590-that is connected to solenoid valve 382. The switches may beoperated directly by the operator or may be operated by any suitablelinkage to close the switches to provide the schedule of solenoid valveoperation shown in FIG. 7. This schedule effects conditioning of thetransmission in neutral, the first, second and third forward drives,automatic drive and the two reverse drives.

TRANSMISSION CONTROL OPERATION The control system described above isoperable to provide automatic shifting between all of the forward drivesand also to provide manual. shifting between the three lowest speedrange forward drives and the two reverse drives. The schedule ofoperation available is shown in FIG. 7 with the letter X denoting whichsolenoid valves are energized in each operation Neutral For neutral, thevehicle operator closes the switch 576 to energize the solenoid valve329 which controls the neutral valve 312 and also closes the switch 574to energize the solenoid valve 485 which controls the directional valve461. When the engine is started, the input pump supplies fluid to mainline 124 where it passes through the filter 129 before being deliveredto the main pressure regulator valve 132, the secondary main pressureregulator valve 154, the neutral valve 312, the directional valve 461and the brake apply valve 228. The secondary main pressure regulatorvalve 154 delivers fluid to the secondary main line 161 which directsthe flow it receives to the T.V. valve 291, the lockup shift valve 524,the neutral valve 312, the forward-reverse inhibitor valve 484, themanual valve 441, all of the pilot valves 386, 402 and 422, the 2-3shift valve 348 and the l2 shift valve 364. Since the vehicle is atrest, there is no G1 pressure provided to the G1 line 282 and thus thelockup shift valve 524 will be held in its release position withdelivery of T.V. pressure to the T.V. line 304 from the T.V. valve 291.Thus, the lockup clutch motor 534 is exhausted by the lockup shift valve524 so that the lockup clutch 35 is disengaged and no lockup signalpressure is' delivered to the line 536 from the secondary main line 161so that the main pressure regulator valve 132 regulates the mainpressure in main line 124 at the high value. At the neutral valve 312,with the solenoid valve 329 energized and thus open while this valvesother solenoid valve 325 is deenergized and thus closed, the fluiddelivered to chamber 328 of this valve is prevented from building tosecondary main line pressure while main line pressure is delivered tothe other chamber 318 where it builds to its full value to aid spring317 in holding the neutral valve in its neutral position as shown. Thus,main line pressure is prevented from being delivered to the range mainline 319 and thus the downstream shift valves 333, 348 and 364, therange main line 319 then being connected to" exhaust port 321. At thedirectional valve 461 with the solenoid valve 485 energized and thusopen while this other valves solenoid valve 490 is deenergized and thusclosed, fluid pressure cannot build in chamber 468 but does build inchamber 482 to full main line pressure to effect movement of thedirectional valve against its spring bias to the reverse drive position.Fluid in secondary main line 161 is directed to chamber 482 by theforward-reverse inhibitor valve 494 which is held inits shift-permitposition by the spring 499 since there is no G2 pressure with thevehicle at rest. The other reverse drive bias chamber 481 is exhaustedby the exhaust port 508 of the-ford-reverse inhibitor valve 494. Withthe directional valve 461 thus in its reverse drive position, the clutch48 is disengaged because of this valve condition and the clutch 50 isdisengaged since there is no fluid supply to the l2 shift valve feedline 359.

At the manual valve 441, the fluid delivered to chamber 451 bythesecondary main line 161 builds to full secondary main line pressuresince the solenoid valve 455 is deenergized and thus the manual valvemoves against its spring bias to its cutoff or blocking position inwhich it prevents delivery of secondary main line pressure to line 401and thus to downstream pilot valves 386, 402 and 422 and insteadconnects line 401 to exhaust port 458. Thus, all of the pilot valves386, 402 and 422 will be in their downshift demand positions since thedownshift demand T.V. bias will exceed the G2 pressure bias as long asthere is no vehicle speed and on engine throttle opening.

At the 12 shift valve 364 with the solenoid valve 382 deenergized andthus closed, pressure builds the chamber 381 to full secondary main linepressure to urge the l2 shift valve to its downshift position againstthe bias of spring 368. At the 2-3 shift valve 348, with the solenoidvalve 420 deenergized and thus closed, pressure builds in chamber 361 tofull secondary main line pressureto hold the 2-3 shift valve in itsdownshift position against the bias of spring 352 and thereby providesfor connection to the 2-3 shift valve feed line 341 to the l2 shiftvalve feed line 359. At the 3-4 shift valve 333, the chamber 346 isexhausted'so that the bias of spring 337 holds the 3-4 shift valve inits downshift position providing connection of the then exhausted rangemain line 319 to the 2-3 shift valve feed line 341..Thus, all driveestablishing devices are disen' gaged so that no drive is transmitted tothetransmissions output shafts 12 and 14.

The pressure of the fluid delivered by the main pressure regulator valve132 to the hydrostatic supercharge supply line 148 is regulated by thesupercharge pressure regulator valve 169 to' a value suitable forthehydrostatic steer units control system which forms no part of thisinvention. The pressure of the fluid delivered to the converter supplyline 184 limited to a high value by the converter relief valve 188 sincethere is no lockup ,engagement signal pressure being delivered tochamber 204 by the lockup shift valve 524. Fluid leaving the torqueconverter via the converter return line 207 is directed to the pushstart-diverter valve 208 and is also directed through the cooler 269 tothe brake coolant valve 255. When converter inlet pressure tends toexceed the aforementioned high value the converter relief valve 188 willdeliver fluid to the line 202 which is connected by line 207 downstreamof cooler 269 to the brake coolant valve 255. With the output brakedisengaged, the brake coolant valve 255 is positioned in the positionshown so that only a small amount of fluid is delivered to the lines 274and 275 to provide lubrication of the output brakes while the remainingmajor portion of the fluid is delivered by line 270 to lubricate theother transmission components with the pressure of such lubricationbeing limited by the valve 271. When pressure in the hydrostaticsupercharge supply line 148 has reached its normal regulated value, thispressure acting in chamber 224 of the push start-diverter valve 208 issufficient to move this valve to its flow diverting position so that theoutput pump 121 which is not yet operating since the vehicle is at restis connected to the converter return line 207 upstream of the cooler269. If the output brakes are operated in neutral as service brakes,fluid at main line pressure is delivered from the line 124 to chamber267 of the brake coolant valve 255 upon initial movement of the brakeapply valve 228 so that valve 255 starts delivering fluid to cool theoutput brakes 89 and 94 prior to their engagement with a regulatedpressure which occurs on further movement of the brake apply valve 228,the regulated pressure for the brake engagement being determined by theamount of force applied to the brake apply valve. However, with thevehicle stationary, there is no substantial cooling requirement for theoutput brakes, such cooling requirements becoming substantial only whenthe vehicle is in motion.

Manual Control The first forward drive by manual selection isestablished by the vehicle operator opening the switch 574 so thatsolenoid valve 329 at the neutral valve 312 is then deenergized, andclosing switches 572, 575 and 578 so that the solenoid valves 490, 325and 455 at the directional valve 461, neutral valve 312 and the manualvalve 441, respectively, are energized. With the directional valve 461now moved to its forward drive position engagement of clutch 48 isprovided. At the neutral valve 312 with solenoid valve 325 now energizedand thus open while solenoid valve 329 is deenergized and thus closed,pressure builds in chamber 328 to full secondary main line pressure sothat the neutral valve is then moved against the bias of spring 317 toits drive-permit position in which it connects the main line 124 to therange main line 319. At the manual valve 441, with the. solenoid valve455 energized and thus open, pressure is prevented from building inchamber 451 to full secondary main line pressure and thus the manualvalve is moved to its manual select position by the bias of spring 466.In the manual select position, the manual valve 441 connects thesecondary main line 161 to the line 401 so that secondary main linepressure acts to .hold all of the pilot valves 386, 402 and 422 in theirdownshift demand positions against the upshift demand bias provided byG2 pressure that is developed on motion of the vehicle. With the 3-4pilot valve 386 in its downshift demand position connecting line 397 toexhaust port 396, the 34 shift valve 333 is held by spring 337 in itsdownshift position connecting the range main line 391 to the 2-3 shiftvalve feed line 341.

At the 2-3shift valve 348, full secondary main line pressure exists inchamber 361 since the 2-3 pilot valve 402 is in its downshift demandposition with the solenoid valve 420 deenergized and thus closed topermit such pressure buildup. Thus the 2-3 shift valve 348 is held byfull secondary main line pressure in its downshift position against thebias of spring 352 to connect the 2-3 shift valve feed line 341 to thel-2 shift valve feed line 359. At the l-2 shift valve 364, with thesolenoid valve 382 deenergized and thus closed, pressure in chamber 381is maintained at full secondary main line pressure to hold the l-2 shiftvalve in its downshift position against the bias of spring 368 so thatthe l-2 shift valve feed line 359 is connected to the line 378. Thus,fluid at main line pressure is delivered to the fluid motor 379 toengage the brake 66 which together with the engagement of clutch 48establishes the first forward drive.

With the first forward drive thus established manually and on theoperator opening the engine throttle, the vehicle will move in theforward direction by the power transmitted to the two output shafts l2and 14. The G2 pressure in G2 line 289 increases with increasingtransmission output speed and acts on all of the pilot valves 386, 402and 422 to urge an upshift but such governor pressure bias is notnormally sufficient to counteract the secondary 'main line pressure biaswhich holds all of these valves in their downshift demand position. Thepilot valves will however upshift at an overspeed of percent, forexample, in their respective drives such as might occur on downhillcoast. In the first forward drive, the G1 pressure developed in the G1line will move the lockup shift valve 524 to its lockup position againstthe T.V. bias but the lockup clutch 35 is not engaged since there isfluid supply to line 538 in the first forward drive.

The second forward drive by manual selection is 1 established by thevehicle operator maintaining the switches 572, 575 and 578 closed tothus maintain the solenoid valves 490, 325 and 455 energized and-thusopen, and additionally closing the switch 580 so that solenoid valve 382is then energized and thus open. At the l-2 shift valve 364 with thesolenoid valve 382 open, pressure in chamber 381 is exhausted so thatthe bias of spring 368 moves the l-2 shift valve 364 to its upshiftposition in which it connects the l-2 shift valve feed line 359 to theline 372 while connecting the line 378 to the exhaust port 376. Thus,the motor 379 is exhausted to disengage the brake 66 while the motor 374is pressurized to engage the brake 78. Since there have been no otherchanges in the control system the clutch 48 has remained engaged andthus the second forward drive is established. With the second forwarddrive thus established, the vehicle can continue to be accelerated butin a higher'speed range. The lockup shift valve 524 is calibrated sothat within the speed range of the second forward drive, the biasprovided by G1 pressure in chamber 530 overcomes the bias provided byT.V. pressure in chamber 532 to move the lockup shift valve 524 to itslockup engage position. With the lockup shift valve 524 thus conditionedin its lockup engage position, fluid from the line 372 that is connectedto operate the brake 78 is delivered sequentially through the 2-3 and3-2 lockup timer valve 541 and 3-4 and 43 lockup timer valve 542 to theline 538 which is then connected to the line 533 to deliver fluid to themotor 534 to engage the lockup clutch 35. On such flow through the timervalves 541 and 542, the respective valve elements 544 and 556 will bemoved, if they have not previously been moved, to the positions shownand held there by the pressure of the fluid being deliveredtherethrough. Whenever lockup clutch 35 is engaged, the lockup shiftvalve 524 which is then in its engage position delivers secondary mainline pressure to line 536 and thus to the respective chambers 152 and204 of the main pressure regulator valve 132 and converter relief valve188 to reduce the main line pressure and converter inlet pressure duringconverter lockup operation.

The third forward drive by manual selection is established by thevehicle operator leaving the switches 572, 575 and 578 closed, openingthe switch 580 and closing the switch 579. Thus, the solenoid valves490,

325 and 455 at the directional valve 461, neutral valve 312, and manualvalve 441 remain energized and thus open while the solenoid valve 382 atthe 1-2 shift valve 364 is deenergized and thus closed and the solenoidvalve 420 at the 2-3 shift valve 348 is energized and thus open. Thus,the directional valve 461 remains in its forward drive position, theneutral valve 312 remains in its drive-permit position and the manualvalve 441 remains in its manual drive position. With the solenoid valve382. thus closed, the secondary main pressure builds in chamber 381 toforce the l-2 shift valve 364 back to its downshift position connectingline 372 to the exhaust port 384 and also to exhaust port 358 so thatthe motor 374 is exhausted to release the brake 78. At the 2-3 shiftvalve 348 with the opening of the solenoid valve 420, chamber .361 isrelieved of the secondary main pressure so that spring 352 then movesthe 2-3 shift valve 348 to its upshift position in which it connects the1-2 shift valve feed line 359 to the exhaust port 358 while connectingthe 2-3 shift valve feed line 341 to the line 356 which is connected tothem motor 357 that operates the brake 52 andis also connected to the2-3 and 3-2 lockup timer valve 541. As the motor 357 is being filledwith fluid at main pressure to engage the brake 52, the line 372 andthus the lower end of bore 546 of the 2-3 and 3-2 lockup timer valve 541is being exhausted by the 1-2 shift valve 364. This causes downwardmovement of the valve element 544 which movement momentarily interruptsthe feed to the lockup shift valve 524. On the shift the G1 pressuredrops permitting the T.V. pressure to move the lockup shift valve 524 toits disengage position. Thus, the lockup clutch 35 is momentarilydisengaged during the shift from second to the third forward drive sothat the hydraulic path through the torque converter 16 is madeavailable to cushion the shift change. With the shift completed, normalcommunication for the main line pressure feed to engage the lockupclutch 35 is restored with the G1 pressure increased to return thelockup shift valve 524 to its lockup position so that the lockup clutchis again engaged with full main line pressure.

Downshifting by manual selection is accomplished by reversing thesequence of operation described above. On downshifting from the'third tothe second forward drive, the 2-3 and 3-2 lockup timer valve 541 willmomentarily interrupt feed for the engagement of the lockup clutch 35like on the upshift from second to third forward drive since line 372will then be pressurized while line 356 is being exhausted.

It will be recalled that in the three forward drives provided by manualselection the manual valve 441 is maintained in its manual selectposition in which it delivers secondary main pressure to all of thepilot valves 386, 402 and 422. This secondary main pressure aids T.V.pressure in biasing all of the pilot valves to their downshift demandpositions against the upshift demand bias provided by G2 pressure. Thisadditive secondary main pressure downshift demand bias on the pilotvalves prevents these valves from moving to their upshift demandpositions except at vehicle speeds beyond those normally encountered ineach of the three lowest speed range drives. As a result, if manualdownshifts are selected while the vehicle is operating at a speed higherthan a predetermined maximum downshift speed, the G2 pressure holdsengagement of the higher speed range drive until vehicle speed decreasesbelow this maximum downshift speed. When the vehicle is operating in thethird forward drive by manual selection and the vehicle operator thenselects the second forward drive, the 2-3 pilot valve 402 is held in itsupshift demand position by the G2 pressure in chamber 409 to connectchamber 361 of the 2-3 shift valve 348 to exhaust port 416 until thevehicle speed and thus G2 pressure is reduced to a value suitable foroperation in the second forward drive whereupon the 2-3 pilot valve 402is then moved to its downshift demand position and effects establishmentof the 2-3 shift valve 348 in its downshift position since solenoidvalve 420 is closed. When the vehicle is operating in the second forwarddrive and the operator then selects the first forward drive, the l-2pilot valve 422 is held in its upshift demand position to exhaustchamber 381 of the l-2 shift valve 364 to maintain this shift valve inits upshift position until vehicle speed is reduced to a value suitablefor operation in the first forward drive whereupon the l-2 pilot valve422 is then moved to its downshift demand position and effectsestablishment of the l-2 shift valve 364 in its downshift position sincesolenoid valve 382 is closed.

The first reverse drive is established by the vehicle operator closingthe switches 574, 575 and 578 to energize. and thus open the solenoidvalves 485, 325 and 455 at the directional valve 461, neutral valve 312,and manual valve 441, respectively. All other solenoid valves aredeenergized and thus closed. At the directional valve 461 with thesolenoid valve 485 thus open, the chamber 468 is exhausted so that theonly upward or forward drive bias on this valve is provided by spring466. The pressure feed to the chamber 482 at the opposite end of thedirectional valve 461 is under the control of the forward-reverseinhibitor valve 494 which is normally held by spring 499 in itsshift-permit position. The forward-reverse inhibitor valve 494 is biasedto its shift-prevent position by G2 pressure acting in chamber 506 andas long as vehicle speed is below the maximum speed suitable for rapidvehicle motion reversal, the forward-reverse inhibitor valve 494 remainsin its shift-permit position to deliver secondary main line pressure tochamber 482 of the directional valve 461. Since solenoid valve 490 isclosed, pressure builds in chamber 482 to bias the directional valve toits reverse drive position in which it connects the l-2 shift valve feedline 359 to the line 474 so that fluid may be supplied to motor 476 toengage the clutch 50 on fluid supply to the l-2 shift valve feed line359. At the manual valve 441 with the solenoid valve 455 open, pressureis prevented from building in chamber 451 so that the spring 446 holdsthe manual valve in its manual select position. In this manual valveposition the secondary main line pressure is delivered to all the pilotvalves to bias them to their downshift demand positions. At the neutralvalve 312 with the solenoid valve 325 open while the solenoid valve 329is closed, pressure builds in the chamber 328 to full secondary mainline pressure to move the neutral valve to its drive-permit position inwhich it connects the main line 124 to the range main line 319. With allof the pilot valves in their downshift demand positions, all of theshift valves are thus conditioned in their downshift positions. Thus,the l-2 shift valve feed line 359 is supplied with main line pressureand since this line is now connected to line 474 by the directionalvalve 461, clutch 50 is engaged. With the l-2 shift valve 364 in itsdownshift position, fluid at main line pressure is also delivered fromthe -l 2 shift valve feed line 359 to line 378 to thus engage the brake66 like in the manual selection of the first forward drive previouslydescribed. Thus, both clutch 50 and brake 66 are engaged and the firstreverse drive is established so that upon opening the engine throttle,the vehicle is moved in the reverse direction.

In the first reverse drive and from zero up to the maximum vehicle speedsuitable for vehicle motion in reverse, G2 pressure acting in chamber506 of the forward-reverse inhibitor valve 494 is not sufficient toovercome thev bias of spring 499 so that the forwardreverse inhibitorvalve remains in its shift-permit posi-

1. In a control system for a transmission providing a plurality ofdifferent speed range drives the combination of a plurality of fluidpressure operated drive engaging means each operable on fluid pressuredelivery thereto to effect establishment of a drive, a fluid pressuresource, throttle pressure valve means operatively connected to saidfluid pressure source for providing a throttle pressure that changeswith transmission torque demand, governor means operatively connected tosaid fluid pressure source for providing a governor pressure thatchanges with transmission output speed, shift valve means conditionableto operatively connect said fluid pressure source to each of said driveengaging means, pilot valve means responsive to both said governorpressure and said throttle pressure to control fluid pressure from saidfluid pressure source to act on and condition each said shift valvemeans to automatically establish drive according to output speed andtorque demand, and manually controlled electrically operated valve meansfor controlling fluid pressure from said fluid pressure source to act onand condition each said shift valve means to establish driveirrespective of torque demand.
 2. In a control system for a transmissionproviding a plurality of different speed range drives the combination ofa plurality of fluid pressure operated drive engaging means eachoperable on fluid pressure delivery thereto to effect establishment of adrive, a fluid pressure source, throttle pressure valve meansoperatively connected to said fluid pressure source for providing athrottle pressure that changes with transmission torque demand, governormeans operatively connected to said fluid pressure source for providinga governor pressure that changes with transmission output speed, shiftvalve means conditionable to operatively connect said fluid pressuresource to each of said drive engaging means, pilot valve meansresponsive to both said governor pressure and said throttle pressure tocontrol fluid pressure from said fluid pressure source to act on andcondition each said shift valve means to automatically establish driveaccording to output speed and torque demand, and manually controlledelectrically operated valve means for controlling fluid pressure fromsaid fluid pressure source to act on and condition each said shift valvemeans to establish drive irrespective of torque demand with automaticdownshifting by said shift valve means under control of said pilot valvemeans according to output speed from a higher speed range drive to amanually selected drive above a predetermined output speed in the higherspeed range drive.
 3. In a control system for a transmission providing aplurality of different speed range drives the combination of a pluralityof fluid pressure operated drive engaging means each operable on fluidpressure delivery thereto to effect establishment of a drive, a fluidpressure source, throttle pressure valve means operatively connected tosaid fluid pressure source for providing a throttle pressure thatchanges with transmission torque demand, governor means operativelyconnected to said fluid source for providing a governor pressure thatchanges with transmission output speed, shift valve means conditionableto operatively connect said fluid pressure source to each of said driveengaging means, pilot valve means responsive to both said governorpressure and said throttle pressure to control fluid pressure from saidfluid pressure source to act on and condition each said shift valvemeans to automatically establish drive according to output speed andtorque demand, manually controlled electrically operated valve means forcontrolling fluid pressure from said fluid pressure source to act on andcondition each said shift valve means to establish drive irrespective oftorque demand and said pilot valve means including means responsive tofluid pressure from said fluid pressure source for preventing said shiftvalve means from effecting a shift from a manually selected drive to ahigher speed range drive.
 4. In a control system for a transmissionproviding a plurality of different speed range drives the combination ofa plurality of fluid pressure operated drive engaging means eachoperable on fluid pressure delivery thereto to effect establishment of adrive, a fluid pressure source, throttle pressure valve meansoperatively connected to said fluid pressure source for providing athrottle pressure that changes with transmission torque demand, governormeans operatively connected to said fluid pressure source for providinga governor pressure that changes with transmission output speed, shiftvalve means conditionable to operatively connect said fluid pressuresource to each of said drive engaging means, pilot valve meansresponsive to both said governor pressure and said throttle pressure tocontrol fluid pressure from said fluid pressure source to act on andcondition each said shift valve means to automatically establish driveaccording to output speed and torque demand, manually controlledelectrically operated valve means for controlling fluid pressure fromsaid fluid pressure source to act on and condition each said shift valvemeans to establish drive irrespective of torque demand, neutral valvemeans for selectively preventing and permitting drive shifting by saidshift valve means by controlling connection between said fluid pressuresource and said shift valve means, and manually controlled electricallyoperated valve means for controlling fluid pressure from said fluidpressure source to act on and condition said neutral valve means toselectively prevent and permit drive shifting by said shift valve meansand on electric power interruption maintaining the then-existing neutralvalve condition.
 5. In a control system for a transmission providing aplurality of different forward speed range drives and at least onereverse drive, the combination of a plurality of fluid pressure operateddrive engaging means operable on selective fluid pressure deliverythereto to effect establishment of forward drives and a reverse drive, afluid pressure source, throttle pressure valve means operativelyconnected to said fluid pressure source for providing a throttlepressure that changes with transmission torque demand, governor meansoperatively connected to said fluid pressure source for providing agovernor pressure that changes with transmission output speed,directional valve means, shift valve means, said directional valve meansand said shift valve means conditionable to operatively connect saidfluid pressure source to said drive engaging means to establish thedrives, pilot valve means responsive to both said governor pressure andsaid throttle pressure to control fluid pressure from said fluidpressure source to act on and condition each said shift valve means toautomatically establish forward drive according to output speed andtorque demand, manually controlled electrically operated valve means forcontrolling fluid pressure from said fluid pressure source to act on andcondition each said shift valve means to manually select forward driveirrespective of torque demand neutral valve means for selectivelypreventing and permitting drive shifting by said shift valve means bycontrolling connection between said fluid pressure source and said shiftvalve means, manually controlled electrically operated valve means forcontrolling fluid pressure from said fluid pressure source to act on andcondition said neutral valve means to selectively prevent and permitforward drive shifting by said shift valve means and on eleCtrical powerinterruption during drive maintaining the then-existing neutral valvedrive permitted condition, and manually controlled electrically operatedvalve means for controlling fluid pressure from said fluid pressuresource to act on and condition said directional valve means toselectively establish forward and reverse drive and on electrical powerinterruption during either forward or reverse drive maintaining thethen-existing drive.
 6. In a control system for a transmission providinga plurality of different speed range drives the combination of aplurality of fluid pressure operated drive engaging means each operableon fluid pressure delivery thereto to effect establishment of a drive,an input pump providing a fluid pressure source, an output pumpproviding another fluid pressure source, throttle pressure valve meansoperatively connected to said fluid pressure sources for providing athrottle pressure that changes with transmission torque demand, governormeans operatively connected to said fluid pressure sources for providinga governor pressure that changes with transmission output speed, shiftvalve means conditionable to deliver fluid pressure from both saidsources to each of said drive engaging means, pilot valve meansresponsive to both said governor pressure and said throttle pressure tocontrol fluid pressure from both said sources to act on and conditioneach said shift valve means to automatically establish drive accordingto output speed and torque demand, manually controlled electricallyoperated valve means for controlling fluid pressure from both saidsources to act on and condition each said shift valve means to establishdrive, transmission output brake means, and means controlled by thefluid pressure delivered to one of said drive engaging means and alsofluid pressure from said input pump for positively diverting fluid fromsaid output pump to cool said transmission output brake means in atleast the highest speed range drive provided by the automatic and manualselection.
 7. In a control system for a transmission providing aplurality of different forward speed range drives and at least tworeverse drives the combination of a plurality of fluid pressure operateddrive engaging means each operable on fluid pressure delivery thereto toeffect establishment of a drive, throttle pressure valve meansoperatively connected to said fluid pressure sources for providing athrottle pressure that changes with transmission torque demand, governormeans operatively connected to said fluid pressure source for providinga governor pressure that changes with transmission output speed,directional valve means, shift valve means, said directional valve meansand said shift valve means conditionable to operatively connect saidfluid pressure source to said drive engaging means to establish thedrives, pilot valve means responsive to both said governor pressure andsaid throttle pressure to control fluid pressure from said fluidpressure source to act on and condition said shift valve means toautomatically establish forward drives according to output speed andtorque demand, manually controlled electrically operated valve means forcontrolling fluid pressure from said fluid pressure source to act on andcondition each said shift valve means to manually select forward driveirrespective of torque demand, neutral valve means for selectivelypreventing and permitting drive shifting by said shift valve means bycontrolling connection between said fluid pressure source and said shiftvalve means, manually controlled electrically operated valve means forcontrolling fluid pressure from said fluid pressure source to act on andcondition said neutral valve means to selectively prevent and permitforward drive shifting by said shift valve means and on electric powerinterruption maintaining the then-existing neutral valve condition,manual valve means for controlling fluid pressure from said fluidpressure source to act on and condition said pilot valve means toprevent upshift opEration after downshift operation during manuallyselected drive operation, manually controlled electrically operatedvalve means for controlling fluid pressure from said fluid pressuresource to act on and condition said directional valve means to shiftbetween forward and reverse drive and also between the reverse drivesand on electric power interruption maintaining the then-existing drivein either forward or reverse and inhibitor valve means responsive tosaid governor pressure for controlling fluid pressure from said fluidpressure source to act on and condition said directional valve means toprevent shifting between forward drive and reverse drive above apredetermined output speed.
 8. In a control system for a transmissionproviding a plurality of different speed range drives the combination ofa plurality of fluid pressure operated drive engaging means eachoperable on fluid pressure delivery thereto to effect establishment of adrive, a fluid pressure source, throttle pressure regulator valve meansoperatively connected to said fluid pressure source for providing athrottle pressure increasing with increasing transmission torque demand,governor means operatively connected to said fluid pressure source forproviding a governor pressure increasing with increasing transmissionoutput speed, shift valve means operatively connected to each of saiddrive engaging means, all of said shift valve means operativelyconnected in series to said fluid pressure source, the furthestdownstream shift valve means operable in a downshift position toestablish fluid delivery to the drive engaging means that establishesthe lowest speed range drive and in an upshift position to exhaust fluidfrom the last-mentioned drive engaging means while establishing fluiddelivery to the drive engaging means that establishes the next higherspeed range drive, each of the other of said shift valve means operablein a downshift position to establish fluid delivery to the immediatedownstream shift valve means and in an upshift position to exhaust fluidfrom the immediate downstream shift valve means while establishing fluiddelivery to the connected drive engaging means, spring means fornormally biasing each of said shift valve means to one of said shiftpositions, means for delivering fluid pressure from said fluid pressuresource to bias each of said shift valve means to the other of said shiftpositions, pilot valve means corresponding to each of said shift valvemeans and responsive to both said throttle pressure and governorpressure for controlling the pressure bias on the associated shift valvemeans to effect sequential upshifting and downshifting of the drives inaccordance with torque demand and output speed and manually controlledelectrically operated valve means corresponding to each of said shiftvalve means for relieving the fluid pressure bias on the associatedshift valve means to select drive.
 9. In a control system for atransmission providing a plurality of different speed range drives thecombination of a plurality of fluid pressure operated drive engagingmeans each operable on fluid pressure delivery thereto to effectestablishment of a drive, a fluid pressure source, throttle pressureregulator valve means operatively connected to said fluid pressuresource for providing a throttle pressure increasing with increasingtransmission torque demand, governor means operatively connected to saidfluid pressure source for providing a governor pressure increasing withincreasing transmission output speed, shift valve means operativelyconnected to each of said drive engaging means, all of said shift valvemeans operatively connected in series to said fluid pressure source, thefurthest downstream shift valve means operable in a downshift positionto establish fluid delivery to the drive engaging means that establishesthe lowest speed range drive and in an upshift position to exhaust fluidfrom the last-mentioned drive engaging means while establishing fluiddelivery to the Drive engaging means that establishes the next higherspeed range drive, each of the other of said shift valve means operablein a downshift position to establish fluid delivery to the immediatedownstream shift valve means and in an upshift position to exhaust fluidfrom the immediate downstream shift valve means while establishing fluiddelivery to the connected drive engaging means, spring means fornormally biasing each said shift valve means to one of said shiftpositions, manually controlled electrically operated valve means fordelivering fluid pressure from said fluid pressure source to bias eachof said shift valve means to the other of said shift positions, pilotvalve means corresponding to each of said shift valve means andresponsive to both said throttle pressure and governor pressure forcontrolling the pressure bias on the associated shift valve means toeffect sequential upshifting and downshifting of the drives inaccordance with torque demand and output speed, manually controlledelectrically operated valve means corresponding to each of the shiftvalve means for relieving the fluid pressure bias on the associatedshift valve means to select drive, manually controlled electricallyoperated manual valve means for selectively delivering fluid pressureduring manual shifting from said fluid pressure source to all of saidpilot valve means and each of said pilot valve means including pressureresponsive means responsive to the pressure delivered by said manualvalve means to prevent said shift valve means for effecting a shift froma manually selected drive to a higher speed range drive.
 10. In acontrol system for a transmission providing a plurality of differentspeed range drives the combination of a plurality of fluid pressureoperated drive engaging means each operable on fluid pressure deliverythereto to effect establishment of a drive, a fluid pressure source,throttle pressure regulator valve means operatively connected to saidfluid pressure source for providing a throttle pressure increasing withincreasing transmission torque demand, governor means operativelyconnected to said fluid pressure source for providing a governorpressure increasing with increasing transmission output speed, shiftvalve means operatively connected to each of said drive engaging means,all of said shift valve means operatively connected in series to saidfluid pressure source, the furthest downstream shift valve meansoperable in a downshift position to establish fluid delivery to thedrive engaging means that establishes the lowest speed range drive andin an upshift position, to exhaust fluid from the last-mentioned driveengaging means while establishing fluid delivery to the drive engagingmeans that establishes the next higher speed range drive, each of theother of said shift valve means operable in a downshift position toestablish fluid pressure delivery to the immediate downstream shiftvalve means and in an upshift position to exhaust fluid from theimmediate downstream shift valve means while establishing fluid deliveryto the connected drive engaging means, means normally biasing each ofsaid shift valve means to one of the shift positions, each of said shiftvalve means having pressure responsive means responsive to fluidpressure to bias the shift valve means to the other shift position,pilot valve means corresponding to each of said shift valve means andresponsive to both said throttle pressure and governor pressure fordelivering fluid pressure from said fluid pressure source to thepressure responsive means of the associated shift valve means to biasthe associated shift valve means from said one position to said otherposition to effect sequential upshifting and downshifting of the drivesin accordance with torque demand and output speed and manuallycontrolled electrically operated valve means corresponding to each ofsaid shift valve means for relieving the fluid pressure on theassociated shift valve means to condition the associated shift valveMeans in said one position.
 11. In a control system for a transmissionproviding a plurality of different speed range drives the combination ofa plurality of fluid pressure operated drive engaging means eachoperable on fluid pressure delivery thereto to effect establishment of adrive, a fluid pressure source, throttle pressure regulator valve meansoperatively connected to said fluid pressure source for providing athrottle pressure increasing with increasing transmission torque demand,governor means operatively connected to said fluid pressure source forproviding a governor pressure increasing with increasing transmissionoutput speed, shift valve means operatively connected to each of saiddrive engaging means and to said fluid pressure source, each of saidshift valve means operable in a downshift position to establish fluiddelivery to the connected drive engaging means and in an upshiftposition to exhaust fluid from the connected drive engaging means, meansfor normally biasing each said shift valve means to one of said shiftpositions, means for delivering fluid pressure to act on each of saidshift valve means to urge said shift valve means to the other shiftposition, pilot valve means corresponding to each of said shift valvemeans and responsive to both said throttle pressure and governorpressure for relieving the pressure bias on the associated shift valvemeans in accordance with torque demand and output speed to effectsequential upshifting and downshifting of the drives, manuallycontrolled electrically operated valve means corresponding to each ofsaid shift valve means for relieving the fluid pressure bias on theassociated shift valve means regardless of the operation of theassociated pilot valve means to control the associated shift valve meansto select drive and manual valve means operatively connected to saidfluid pressure source for selectively delivering a downshift demandpressure to all of said pilot valve means,.
 12. In a control system fora transmission providing a plurality of different speed range drives thecombination of a plurality of fluid pressure operated drive engagingmeans each operable on fluid pressure delivery thereto to effectestablishment of a drive, a fluid pressure source, throttle pressureregulator valve means operatively connected to said fluid pressuresource for providing a throttle pressure increasing with increasingtransmission torque demand, governor means operatively connected to saidfluid pressure source for providing a governor pressure increasing withincreasing transmission output speed, shift valve means operativelyconnected to each of said drive engaging means, all of said shift valvemeans operatively connected in series to said fluid pressure source, thefurthest downstream shift valve means operable in a downshift positionto establish fluid delivery to the drive engaging means that establishesthe lowest speed range and in an upshift position to exhaust fluid fromthe last-mentioned drive engaging means while establishing delivery offluid to the drive engaging means that establishes the next higher speedrange drive, each of the other of said shift valve means operable in adownshift position to establish fluid delivery to the immediatedownstream shift valve means and in an upshift position to exhaust fluidfrom the immediate downstream shift valve means while establishing fluiddelivery to the connected drive engaging means, means for normallybiasing each said shift valve means to one of said shift positions,means for delivering fluid pressure to act on each of said shift valvemeans to urge said shift valve means to the other shift position, pilotvalve means corresponding to each of said shift valve means andresponsive to both said throttle pressure and governor pressure forrelieving the pressure bias on the associated shift valve means inaccordance with torque demand and output speed to effect sequentialupshifting and downshifting of the drives, manually controlledelectrically oPerated valve means corresponding to each of said shiftvalve means for relieving the fluid pressure bias on the associatedshift valve means regardless of the operation of the associated pilotvalve means to control the associated shift valve means to select drive,manual valve means operatively connected to said fluid pressure sourcefor selectively delivering a downshift demand pressure to all of saidpilot valve means, biasing means normally biasing said manual valvemeans to a downshift demand pressure delivery position, means normallydelivering fluid pressure from said fluid pressure source to bias saidmanual valve means to a position preventing downshift demand pressuredelivery, manually controlled electrically operated valve means forrelieving the fluid pressure bias on said manual valve means toestablish downshift demand pressure delivery to said pilot valve meansand each said pilot valve means having means responsive to saiddownshift demand pressure from said manual valve means to condition thepilot valve means to demand the downshift position of the associatedshift valve means.
 13. In a control system for a transmission providinga plurality of different speed range drives including both forward andreverse drive the combination of a plurality of fluid pressure operateddrive engaging means each operable on fluid pressure delivery thereto toeffect establishment of a drive, a fluid pressure source, throttlepressure regulator valve means operatively connected to said fluidpressure source for providing a throttle pressure increasing withincreasing transmission torque demand, governor means operativelyconnected to said fluid pressure source for providing a governorpressure increasing with increasing transmission output speed, shiftvalve means operatively connected to each of said drive engaging meansand to said fluid pressure source, each of said shift valve meansoperable in a downshift position to establish fluid delivery to theconnected drive engaging means and in an upshift position to exhaustfluid from the connected drive engaging means, directional valve meansfor cooperating with said furthest downstream shift valve means toselectively deliver fluid to one of two of said drive engaging means toeffect in a forward drive position establishment of all of the forwarddrives and in a reverse drive position establishment of reverse drive,spring means normally biasing said directional valve means to saidforward drive position, said directional valve means having pressureresponsive means responsive to a forward bias pressure derived from saidfluid pressure source only in said forward drive position to urge saiddirectional valve means to said forward drive position, manuallycontrolled electrically operated valve means for relieving any forwardbias pressure acting to urge said directional valve means to saidforward drive position, forward-reverse inhibitor valve means, springmeans for normally biasing and forward-reverse inhibitor valve means toa shift permit position to deliver a first reverse bias pressure derivedfrom said fluid pressure source to said directional valve means, saidforward-reverse inhibitor valve means having pressure responsive meansresponsive to said governor pressure for urging said forward-reverseinhibitor valve means to a shift inhibit position preventing delivery ofsaid first reverse bias pressure to said directional valve means whileproviding for delivery to said directional valve means of a secondreverse bias pressure derived from the fluid delivered by saiddirectional valve means to establish reverse drive, said directionalvalve means having means responsive to said second reverse bias pressureto urge said directional valve means to said forward position andmanually controlled electrically operated valve means for relieving saidfirst reverse bias pressure on said directional valve means.
 14. In acontrol system for a transmission providing a plurality of differentspeed drives including both Pg,104 forward and reverse drive thecombination of a plurality of fluid pressure operated drive engagingmeans each operable on fluid pressure delivery thereto to effectestablishment of a drive, a fluid pressure source, throttle pressureregulator valve means operatively connected to said fluid pressuresource for providing a throttle pressure increasing with increasingtransmission torque demand, governor means operatively connected to saidfluid pressure source for providing a governor pressure increasing withincreasing transmission output speed, shift valve means operativelyconnected to each of said drive engaging means, all of said shift valvemeans operatively connected in series to said fluid pressure source, thefurthest downstream shift valve means operable in a downshift positionto establish fluid delivery to the drive engaging means that establishesthe lowest speed range drive and in an upshift position to exhaust fluidfrom the last-mentioned drive engaging means while establishing fluidpressure delivery to the drive engaging means that establishes the nexthigher speed range drive, each of the other of said shift valve meansoperable in a downshift position to establish fluid delivery to theimmediate downstream shift valve means and in an upshift position toexhaust fluid from the immediate downstream shift valve means whileestablishing fluid delivery to the connected drive engaging means,directional valve means for cooperating with said furthest downstreamshift valve means to selectively deliver fluid to one of two of saiddrive engaging means to effect in a forward drive position establishmentof all of the forward drives and in a reverse drive positionestablishment of reverse drive, spring means normally biasing saiddirectional valve means to said forward drive position, said directionalvalve means having pressure responsive means responsive to a forwardbias pressure derived from said fluid pressure source only in saidforward drive position to urge said directional valve means to saidforward drive position, manually controlled electrically operated valvemeans for relieving any forward bias pressure acting to urge saiddirectional valve means to said forward drive position, forward-reverseinhibitor valve means, spring means for normally biasing saidforward-reverse inhibitor valve means to a shift permit position todeliver a first reverse bias pressure derived from said fluid pressuresource to said directional valve means, said forward-reverse inhibitorvalve means having pressure responsive means responsive to said governorpressure for urging said forward-reverse inhibitor valve means to ashift inhibit position preventing delivery of said first reverse biaspressure to said directional valve means while providing for delivery tosaid directional valve means of a second reverse bias pressure derivedfrom the fluid delivered by said directional valve means to establishreverse drive, said directional valve means having means responsive tosaid second reverse bias pressure to urge said directional valve meansto said forward position and manually controlled electrically operatedvalve means for relieving said first reverse bias pressure on saiddirectional valve means.
 15. In a control system for a transmissionproviding a plurality of different speed range drives including bothforward and reverse drive the combination of a plurality of fluidpressure operated drive engaging means each operable on fluid pressuredelivery thereto to effect establishment of a drive, a fluid pressuresource, throttle pressure regulator valve means operatively connected tosaid fluid pressure source for providing a throttle pressure increasingwith increasing transmission torque demand, governor means operativelyconnected to said fluid pressure source for providing a governorpressure increasing with increasing transmission output speed, shiftvalve means operatively connected to each of said drive engaging means,all of said shift valve means operativeLy connected in series to saidfluid pressure source, the furthest downstream shift valve meansoperable in a downshift position to establish fluid delivery to thedrive engaging means that establishes the lowest speed range drive andin an upshift position to exhaust fluid from the last-mentioned driveengaging means while establishing fluid pressure delivery to the driveengaging means that establishes the next higher speed range drive, eachof the other of said shift valve means operable in a downshift positionto establish fluid delivery to the immediate downstream shift valvemeans and in an upshift position to exhaust fluid from the immediatedownstream shift valve means while establishing fluid delivery to theconnected drive engaging means, directional valve means for cooperatingwith said furthest downstream shift valve means to selectively deliverfluid to one of two of said drive engaging means to effect in a forwarddrive position establishment of all of the forward drives and in areverse drive position establishment of reverse drive, neutral valvemeans, spring means for normally biasing said neutral valve means to aneutral position preventing fluid delivery from said fluid pressuresource to said shift valve means and said directional valve means toprevent establishment of drive in either forward or reverse, saidneutral valve means having pressure responsive means acted on by fluidpressure from said fluid pressure source to bias said neutral valvemeans to a drive position providing fluid delivery to said shift valvemeans and said directional valve means, manually controlled electricallyoperated valve means for relieving any fluid pressure urging saidneutral valve means to said drive position, said neutral valve meanshaving pressure responsive means responsive to fluid pressure from saidfluid pressure source only when said neutral valve means is in saidneutral position to urge said neutral valve to said neutral position,manually controlled electrically operated valve means for relieving anyfluid pressure acting to urge said neutral valve means to said neutralposition, means for relieving pressure acting to urge said neutral valvemeans to said neutral position when said neutral valve means is in saiddrive position, spring means normally biasing said directional valvemeans to said forward drive position, said directional valve meanshaving pressure responsive means responsive to a forward bias pressurederived from said fluid pressure source only in said forward driveposition to urge said directional valve means to said forward driveposition, manually controlled electrically operated valve means forrelieving any forward bias pressure acting to urge said directionalvalve means to said forward drive position, forward-reverse inhibitorvalve means, spring means for normally biasing said forward-reverseinhibitor valve means to a shift permit position to deliver a firstreverse bias pressure derived from said fluid pressure source to saiddirectional valve means, said forward-reverse inhibitor valve meanshaving pressure responsive means responsive to said governor pressurefor urging said forward-reverse inhibitor valve means to a shift inhibitposition preventing delivery of said first reverse bias pressure to saiddirectional valve means while providing for delivery to said directionalvalve means of a second reverse bias pressure derived from the fluiddelivered by said directional valve means to establish reverse drive,said directional valve means having means responsive to said secondreverse bias pressure to urge said directional valve means to saidforward position and manually controlled electrically operated valvemeans for relieving said first reverse bias pressure on said directionalvalve means.